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TRAVELS

IN THE

TWO SICILIES,

AND

SOME PARTS OF THE APENNINES.

Tranflated from the Original Italian of the

ABBE LAZZARO SPALLANZANI,

Profeffor-Reyal of Natural Hiftory in the Univerfity of Pavia, and

Superintendant of the Imperial Mufeum in that City j

Fellow of the Royal Society of London ; and

Member of the Academies of Pruffia,

Stockholm, Gottingen, Turin,

Padua, &c. &c.

IN FOUR VOLUMES. WITH ELEVEN PLATES,

VOL. IIL

LONDON:

IPRINTBD FOR G. G. AND J. ROBlNSOlf;,

TATERNOSTE R-R O W,

1798,

/

CO NT EN T S

OF THE

THIRD VOLUME.

Page

Chap. XYL — ObsERV^TIONS
made in the Interior Parts of Li-
par i^ and fever al of its Mountains i

Chap. XVII. — Felicuda — — ^o

Chap. XVllh-^Maida — > — 124

Chap. XIX. — Obfervations which have
an immediate Relation with the
Volcani^ation of the Eolian IJIes —
Enquiries relative to the Origin of
Bafaltes — — i r 2

Chap.

IV C O K T E it T S.

Page

Chap. XX. — Dlgrejfion relative to the
different Volcanic Produdfions of
the Euganean Mountains — — 216

Rejledfions and Corollaries — — ^o r

Chap, XXI. — ILxperijnental Enquiries
relative to the Nature of the Gafes
ofVolcanoSy and the Caufes of their
Eruptions — — — 317

Chap. XXII. — Difcovery that various
volcanic Products contain Muriatic
Acid — Enquiry how this Acid has
been produced^ and mixed with
the77i — — — 2i^6,

TRAVELS

TRAVELS

IN THE

TWO SICILIES, Sec.

CHAP. XVI.
L I P A R r.

PART THE SECOND,

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

Extremely irregular appearance of this

ijland — No charadler'ifed crater difcover-

able in it — Ccnjediure that the Monte San

Angelo^ and the Monte ddla Guardia, the

VOL. Ill, B higheji

(2 )

h'lghejl mountains in Lipari^ were prQ«
duced by two diJiinEl volcanos — Effloref"
cences of muriate of ammoniac (fal ammo-
niac) in two caverns near the plai?i called
La Valle — Curious volcanic breccia — 'The
volcanic tufa which^ on one fde, covers
the whole mountain of the celebrated Stoves
(or vapour baths) ofLipari^ has every ap^
pearance of having bee?t an earthy cur-'
rent ; and is remarkable for containing
true ligneous coal — ConjeSlural 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
garnets — Comparifon between thefe and
the gar fie ts of Vefuvius — Enamel of the
Liparefe garnets^ which has for its bafe
the horn-fone — Detached lavas in the
road leading to the floves — Volcanic chry-
f&lites in a lava with a hornfione bafe —
Thefe chryfoUtes compared with thofe of
4 Etna —

( 3 )

]E!^na — Large pieces tf red porphyry which
do not feem to have fiiffered fujion — iVo«<?
vfthefe bodies difpofed in currents ; 'whence
it is probable that they have been throiJUfi
into the air by fome volcano— A fpacious
plain of tufa rendered cultivable^ fituated
beyond the Monte della Stufe^ which
affords numerous pieces of the fneft a?td
puref glafs found in Lipari^-^^Local ori-^
gin of this glafs — l^ed of piunices on
the ey:tef2five current of tufa before men-
tioned-—^Stoves of Lipari defcribed— Re-
mains of conflagrations of fulphur under
them^ and in their environs — Prodigious
number of lavas decompofed by the aSiioit
of fulphur eous acid vapours — Oxyde of
pure iron depofited on fome of thefe lavas
^—Variety of colours "which they prefe?it to
the eye — Their decompofition ufually in the
inverfe proportion of the depth of their
maffes — When freed from the decompof-
tion which renders it difficult to afcertain
their nature^ they are ifually found of a
petrofiUceous bafe — This decompofition an
objiacle to their fufion in the furnace — •
. B 2 Expli'

( 4 )

EiXpUcatmi of the caufe of this change — '
Sulphates of lime, var'ioufly coloured^ and
adhering to the decompofed lavas — Iron^
oxydated^ and modified in various manners,
the caufe of the different colours of the
decompofed lavas, and fulphates of lime — =
Difcovery of fever al amorphous and cryf-
tallifed zeolites near the foves — JMy
'which they form ivith mineral acids —
E.mit bright flafhes 'when on the point of
melting, and fwell cojifidcrahly on their
aSiual fufion — 'Terms of comparifon be-
tween thefe zeolites and thofe of other
countries — Their produdiion not by the dry
but the humid voay — Though the zeolites
of fever al volcanized countries are probably
formed within the fea, this does not feein
to be the origin of thofe of Lipari — In-
fiances of zeolites produced in frefJj water
— Sp7-ings of hot water 'which fupply the
baths of Lipari — Another prodigious accu"
mulation of decompofed lavas, and fuU
phures of litne, on the fouthern fide of the
ifland— Perhaps there is no volcaiiized coun-
try in Europe where the fulphureous fumes

ifuing

is)

ijfiiingfr6mfnhterra?iean conjlagratlons are
fo extenfive as at Lipari — Vitrifications of
Campo Bianco^ and the Monte della Cajiag'
na^ 'which are found attached to thofe of
the Monte delie Stufe^ the Monte San An^
geloy and other places — Proofs that almoft
tivo- thirds of Lipari^ which fland is nine^
teen miles and a half in circujnference^ are
compofed of vitrifications — 'The materials
of ivhich this if and is compofed^ prin^
cipally derived from the petrofilex^ fr^^"
fpars in the mafsy and horn-fones^ in part
fiinply fifed by fiihterraneous combufions,
and in a fill greater part vitrified — Not-
ivkhfanding the immenfe accumulations of
this vitrification^ an extraordinary intetifity
of heat not neceffary to be fuppofed — An
exception in the pumices originating from
granite — FeisD Jiotices left us by ancient
authors relative to the fires of Lipari ;.
though we knoiv from indubitable aii-^
thorities, that both the if and and the city
exifled before the Trojan war — No.erup'
lion in this if and defcribed by Hifory:—
Feeble fres, vifble by nighty alone ob-.
B 3 - ferved

( 6 )

Jerved in ancient times — 'This ijland^ the
produce offuhterranean conflagration^ had
.♦ af rived at its greateji dimenftons^ 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 mountains that furround it.
We may thus, at one glance, difcover the
form of thefe inferior mountains, their in-
terchangeable connedion, and the relations
■which they bear to each other, and to the pri-
mary mountain, with other important ob-
je£ts, which, had we firft afcended one of the
lower eminences, we fhould not have been
able to afcertain with equal precifion and
elearnefs.

After, therefore, having made refearches,
■with the greateft diligence, around the fliore
of Lipari, when I proceeded, according to

( 7 )

my original intention, to explore, likewife,
the internal parts of the ifland ; I, firft, af-
cended to the fummit of the Moute 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 diftindl 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 )

that of San Angelo 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, poffibly 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 conjedture, after a
careful examination of the fpot, does not
appear to me improbable. The fame natu-
ralift likewife fuppofes that this mountain,
the height of which is nearly a mile above
the fea, was the firft that was formed in
the illand, through which the volcano burfl
forth, and which ferved as a bafe and fup-
port for the other mountains that were
thrown up afterwards. This opinion is
extremely plaufible ; but the fad: may like-
wife be, in my opiniouj that this mountain,

at

( 9 )

at the time of its produQIon, or very fcon
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-
gefled 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 fea, forming then two
fmall iflands, which afterwards, enlarging
their bafe, united into one ; for it is well
known that other volcanic iflands originall)''
confifted of feveral parts, which afterw^ards
were joined. To thefe two mountains
fubfequent eruptions made new additions,
until at length the whole of the ifland of
Lipari was produced, which, from the ero-
fion of the rains and the fea, is now cer-
tainly lefs than it once was.

From Monte San Angelo, I pafTed to the

Monte

( lo )

Monte della Guardia, which on the fide to-
wards the fea prefents only deep and rug-
ged precipices of lava, and, confequently, is
deprived of all vegetation and verdure ; but
on the land fide, which is oppofite 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 produdt.
While ftanding on the fummit I was ftill
more confirmed in the opinion, that this
mountain is not an acceflary 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 eaft 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 emi-
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 ejeded from them interfered
each other, and confufedly intermixed.
The long and unknown feries of years that
has elapfed fmce thefe eruptions, muft, no
doubt, have contributed to increafe the con-
fufion. Excepting, therefore, fome few
flat places, and prad:icable declivities, which
the inhabitants have rendered cultivable by
great labour, Lipari is a ruinous pile of
horrid precipices, rugged cliffs, and enor-
mous maffes ; and there is no fummit, or
projeding part of a mountain, which does
not exhibit manlfell indications of its fu-
ture fall and deftrudion. The materials of
which thefe ruins are formed are pumices,
enamels, and glafles, which I fhall 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 cuiiolity to vifit a ca-
vern fituated in a fmall plain called La
Valle, about a quarter of a mile to the weft

of

( 12 )

of the City. This cavern has its mouth ia
a rock of decompofed lava, and a man may
walk into it to the diftance of fifty paces.
Its fides are covered with efHorefcences of
muriate of ammoniac, as were, like wife,
thofe of another fmaller cavern in the fame
rock. This fait mufl 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
exifl.

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 fubflance
is an earthy lava, of a blueifh grey, a coarfe
grain, and little hardnefs. In this vs^ere in-
clofed the following bodies :

Firftg

{ 13 )

Firll, fragments of two kinds of lava ;
the one black, of a fcaly fracture, and which
moved the magnetic needle at the diftance
of two lines : the other of a grey ground, a
very rough furface, an unequal fra^burCy
which gave fparks with fteel, and contained
fmall plates of feltfpar. Both were of the
horn-ftone bafe, and emitted a flrong 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.

Fourthly, pieces of a whitilh femi- trans-
parent glafs.

Fifthly, fmall pieces of a colourlefs glafs,
refembling in tranfparency fa<3:itious glafs.
The largefl piece was fourteen lines in

length,

( H )

length, and eight in breadth, and was,' likd
the others, buried in the breccia.

Thefe five fpecies of volcanic produdliong
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 extraded 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 iikewife to the touch, the vitreous lava
appears perfedly fmooth, yet, when viewed
with a lens of a ftrong magnif)'ing 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 conje£l:ured, that
when thefe fubftances were in an ignited
ftate, a current of water might have paiTed
over them ; or that they fuddenly came in

contact

( 15 )

contad with the cold air ; 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
curioflty 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 objeds than
the ftoves themfelves.

Thefe ftoves lie to the weft of the city,
at the diftance of four miles, and fomewhat
beyond the fummit of a mountain, which,
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
work of rain waters, which have made a
deep excavation in an imraenfe mafs of

tufa.

( I6 )

tufa. In more than one place, in this v^orh |
I have fpoken of volcanic tufas, but alinoil
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
flimy 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 v/hen
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,
w^ithout interruption, to beyond the fum-
mit of the Monte della Stufe, or Mountain
of the Stoves. This mountcfln, like moft
of the others, varies confiderably in its dif-

* See Chap. II.

ferent

( '7 )

ferent parts, in one place prefenting 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 exacftly the
fame courfe ; and fometimes curves, and, as
it were, waves on the furface : nor does it
in the leafl: differ in its finuofities and wind-
ings, from the moft completely charad:e-
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 fnnilar eruptions, produced
in the humid way, in the mountains Vefu-
vius, Etna, and Hecla.

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

VOL, III. C when

( i8 )

when its violence had ceafed, the more
heavy bodies muft have fubfided to the
bottom in obedience to the law of gravity,
the lefs heavy have remained above them,
and the Hghteft have occupied the higheft
place ; which, however, is not the fa<3:,
fince, as we ihall fee, at a fmall depth within
the tufa, are found large maffes of lavas,
enamels, and glalTes. But it does not ap-
pear to me improbable that thefe maffes
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 pofition and winding courfe
of this tufa over the back and fides of the
mountain fufficiently prove that it once
£owed : its very nature is a ftrong confir-
mation of this fa6t. It is not an aggrega-
tion of afhes and fand j a mixture of frag-
ments of fhoerls, 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 ftrudure fomewhat 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, when
immerfed in water, greedily imbibes it in
every parr.

In the furnace it firil acquired a reddilh
brown colour, and afterwards the black co-
lour of iron. It became fo hard that it
gave fparks with fteel, without, howeverj
vitrifying, except that its furface aflumed a
kind of vitreous varnifh.

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, notwithftanding the excava-
tions made in it by the rains, J was unable
C^ to

( 20 )

to afcertain Its depth. But in every place
where I could difcover the bottom, I ob-
ferved that it relied 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 unexpeded
phenomenon. On breaking it, its fradures
exhibited fmall black particles, which were
diftindlly recognized to be true coal, from
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
perfedly reduced to coal, as the fibrous
parts of the wood were fl^^ill to be feen.
Thefe <:oals were fmall cylinders from two

or

" ( 21 )

or three lines in length to twelve or four-
teen, and of proportional thicknefs. They
;appeared to have appertained to branches of
trees or Ihrubs ; they are buried in the tufa
at various depths, and are found, though
jhinly 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 flime, 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 diffii-
culties, as the reader, no doubt, already
perceives ; it therefore 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
having burned, but not entirely confumed,
C3 th^

( 22 )

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

It has been aheady faid, that the rapid
defcent of the rain-waters 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 fiflures, 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

( 23 )

In the fame places is found another kind
of enamel containing a great number of
fmali bodies, which I will not abfolutely
affirm to be garnets, becaufe I was not able
to analyze them in the humid way ; but
their external charadlers, together with the
proofs furni(l:ied 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
frad:ures lamellar, perfedly 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 helitate to clafs them with that
fpecies of ftone ; as their not being cryftal-
lized is of little importance, fmce we know
that there are alfo amorphous garnets.

C4 While

C 24 )

While employed in the examination of
thefe flones, I refolved to compare them
with the Vefuvian garnets ; for, in myexcur-
lion to that volcano, I had collected feveral
different fpecies of them on Monte Somma,
which is the ancient Vefuvius. I made fe-
veral experiments on four of thefe, of which
the following is the refult.

The firft fpecies is found in a lava with a
horn-ftone bafe, of a yellowifh grey colour,
an unequal furlace, and of a confiftence
little dif^rent from earthy, from the great
alteration it has undergone ; not, as far as
appears, from fulphurcous exhalations, but
from the action of the atmofphere. The
garnets it contains have likewife fcffered
injury, having lofl a part of their native
luflre, and being eafily broken or crumbled
to pieces from the m.ultitude of minute fif°
fures and cracks in them. They, however,
retain fomewhat of the vitreous charader.
Their colour is between a white and a grey.
At firft view their figure appears perfedlly
globular ; but on extrading them from the
ftone, their matrix, ( which may eafily be

done.'i

( H )

done,) and attentively examining them, they
are found to have facets, though it is not
poffible to afcertain the number of them, as
many of the angles have been defaced by
time. I fhall only oblerve, that having
broken one of thefe garnets into two
equal parts, the perimeter of each half
was otlagonal. This fradure at the fame
time ihewed the texture of the garnet,
which is compofed of very thin circular
leayes. Thefe garnets are of different fizes,
from four lines and a half to one fixth of
jL line.

The furnace reduces the matrix-lava to a
compa(^ 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 contrail: 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 fra<3:ures
than the preceding. Many of them are of a
round figure, and manifeftly fhew a cryftal-
iization 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-exifted com'pletely formed,
and were taken into the moifture from
which the garnet derived its origin.

Thefe garnets are, likewife, 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-black, compa(St, but
not fufficiently hard to give fparks with
fteel. The garnets, which are of a yellow-
i(h white colour, and feme of them four
lines in diameter, for the moft part have
clefts or fiflures, but in fuch a manner that
in the recent fractures the furface refembles
a round 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 compact lava of a horn-ftone bafe,
which emits an argillaceous odour. In the
the furnace it changes into a black ena-
mellar produd, but the garnets remain un-
touched.

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

ture

{ 28 )

ture of the Vefuvian garnets, fo far as it is vi-
treous and lamellar, is fimilar to that of thofe
of Lipari ; but that, when expofed to the fire,
a dilFerence is found between thefe two
ftones, the one eafily melting in the furnace,
and the other proving refradory.

Finding, therefore, that thefe four fpeeies
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 flowly. When the ma-
trix lava flowed like common glafs, the
fmall pieces of garnet within it remained
unchanged 5 but at length fufed, though
without incorporating with the lava, fo as
|:o form a homogeneous whole,

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

fary,

( «9 )

iary *. Sauflure tells us, that a fpotted lava
(lave a oeil de perdrix) which he found on
Monte Somma, acquired,afterfufion, ablack
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 refpedt
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
" affifl:ance of oxygenous gas is here to be
" underftood), and at length, after- continual
*' ebullition, becomes a mafs perfectly fimi-
" lar to quartz, even in its fradure, and
" which crackles in like manner be;tween
" the teeth."

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

* De Produ£lIs Vulcanicls.

t Voyage dans les Alpes, Tom. I,

tioned.

( 30 )

tioned, when they were in a ftate of fufion.
The firft and third, likewife, produced two
fmall mafles refembling quartz, but thofe of
the fecond and fourth variety were fpongy.
It is very poiTible 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, however, do not appear to
me fufHcient to exclude them from being
clafTed with this kind of ftones. It is true,
that iron is ufually contained in garnets 5
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 alutnine,
and that which is leaft 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-
ftituent principles is fufficiently 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 flones,
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

2 mplanted

( 32 )

implanted in it in fuch a manner tluLt they
may be eafily detached without breaking,
leaving the exaiSt imprefiion of their figure
in the enamel. This enamel, which is
compadt, heavy, and of a grey cinereous
colour, is found in detached pieces, both in
the road and in the tufa ; and is the firft
produ6bion 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 ntuations where this peculiar
mixture is found, we likewife meet with an
enaipel containing garnets, fimilar to thofe

above

( 33 )

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 fhall briefly diftinguifli 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 fracture, the colour
of iron, fome appearance of porofity, fufH-
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 compad, rather foft. Almoft
one half of it confifis of rhomboidal felt-
fpars.

VOL, in. D The

( 34 )

The third only differs from the fecond
by being fomewhat more compad:, harder,
and containing fewer feltfpars.

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

All thefe four kinds of lavas are changed,
in the furnace, into vitreous fcori^, 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-ftonei
it is of a dark brown colour, and unequal
in its fractures on account of the fiffures

6 which

( 3S )

which feparate its parts. It is found in de-*
tached pieces, like the four preceding lavasj
but thefe pieces are rare. It gives but few
fparks with fteel, emits a flight argillaceous
odour, and adis on the magnetic needle at
the dlftance of a full line. In confequence
of its numerous fifTures it is rather light,
and when flruek with a hammer is fome-
"What fonorous. 1 orhit to mention fome
fmall fcales of feltfpar incorporated in it,
and proceed to the examination of the chry-
foHteSi

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 between a green and a yel-
low ; but in the recent fraftures they fliine
with much mere brilliant colours. The moft
confpicuous are the golden-yellow, and the
fine grafs-green, with^ which, fometimes, is
mixed a fire-red, tempiered with a tinge of
purple. If thefe chryfolites are expofed to
the immediate light of the fun, and viewed
D 2 under

{ 3(5 )

under certain angles, their colours become
much more lively and bright. Many of
them are amorphous, but fome are quadran-
gular prifms. Their furface, in the fradures,
fhines with a glafly brilliancy, and is fome-
times fmooth, and fometimes rough, accord-
ing as the plates of which the chryfolites
a?e compofed may have been broken. The
fmall fragments of th^m are angular and
fcmi-tranfparent. Thefe chryfolites give
fparks with fteel, and cut glafs nearly like
rock-cryftal. 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 ftones, but are unable to injure them
either in their colours or texture. Oxyge-
nous gas (dephlogifticated air) alone difco-
lours them, and melts them into a globule,
of a white coloury but without briUiancy.

Though

i 37 J

Though it was not known till the pre-
fent time that Lipari afforded volcanic chry-
iblites, 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 refemblances, which it will be proper to
enumerate.

The chryfolites 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
fmall fandy fcales ; but, for the raoft 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 glafly. The mofi: minute parts of thefe
chryfolites exhibited the fame afpe^t 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 in
length, whereas thofe c^eicribed by M. Eau-
jas are fometimes feveral pounds in weight?

They agree, however, with mine in their
infufibility in an extremely adive fire ; foy
thofe on which he made his experiments
refilled the fire of common furnaces, howr
ever violent and continued it might be, ancj
could not be reduced to a ftate of fufion but
by the aid of oxygenous g4S.

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

f he traits of refemblance ^nd difference

between

( 39 )

«

between the Liparefe and Etnean chryfo-
iites 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 prlfms, fometimes with
an hexagonal pyramid ; that their fradure
is partly conchoidal, aad partly lamellar;
that they are harder than quartz ; that they
are more or lefs tranfparent ; that their co-
lour is a green ifh 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 delignedly called the chryfolites of
Lipari, volcanic 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
yefpedtabie authors are of opinion, that the
D 4 volcanic

( 40 )

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

It remains likewife 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 flone 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 maffes, fome of which
weigh feveral thoufand pounds. It is com-
pa6l:, and fcaly in the fractures. The pieces
broken from it are irregular ; the thmneft
are tranfparent at the edges ; and they give
fparks moderately with fteel. The colour
of the bafe has given the feltfpars a reddifh
tinge, as we fee in certain oriental porphy*
ries.

But has this porphyry fuffered fufion, or
is it in its natural Hate, and, at moft, cal-
cined when it was eje<£ted 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 fubflance of this rock
becomes foft, but does not fufe : the felt-
fpars remain unchanged, but the flioerls are
vitrified.

The

■ C . 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 flony 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 arc difpofed 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 ejections.

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-p
tranfparent, of a blackifh colour, and fome
of the fineft and pureft to be found in Li-
pari. As I v/ifhed to difcover the origin of
this fubllancs, 1 caufed the place where it is

found

( 43 )

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

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 prepoffeffion 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
%Q remain long in it, lefs from the heat, for

the

AS

the thermometer Hood at only 48 j degree?^
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 {a.dc^
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 defdtute of
every convenience neceflary to that pur»
pofe ?

When M. Dolomleu vifited them, the
whole ground on which they ftand was pe-^
cetrated with hot vapours, which,,under the
form of a thick fmoke, ifTued from fmali
apertures of about an inch, or two inches,
in diameter. When I was there, circum-
ftances were much changed, as ufually hap-
pens in volcanos, where the prefence of fire
manifefls 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, iffued a thin
flream of fmoke, with a ftrong fulphureous
4 foielU

( 4s )

{tne.il. Having enlarged this aperture, t
found it furrounded by a fmail quantity of
foft fulphures of iron (pyrites) generated by
the union of iron and fulphur. The Ab-
bate Trovatini, whom I have cited in ano-*
ther place, likewife attefts, that, at certain
tiroes, feveral ftreams of fmoke afcended
round the Stoves ; and I (hall 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 fhewn, in Chap. XIII, that the decompo-
fitions of different produ6Vs of Stron:^boli 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 Lipari, I am of opinion, with
M. Dolomieuj are to be attributed to the fame caufe,
the exiflence of which is fufficiently proved by the re-
mains

( 46 )

baths, of which we fhall fpeak below, ^fg
the only places in the whole ifland where
any figns are to be found of as yet unex-*
tinguifhed volcanos.

M. Dolomieu, 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 white tinge, mixed
with yellow, red, violet, and other colours,
which the oxides of iron ufaally produce.
He obferves like wife, that they are coated
with a thick cruft of fulphates of lime (fele-
nite 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 flimy (f^^ngofa) or bog ore.
He then very ingenioufly explains in what
manner, by means of a combination of the

mains of fulphureous fumes, and the quantity of ful-
phates of lime, which I fhall prefently have occaGoa
to defcribe.

fulphuric

( 47 )

flilphuric acid with different earths, the
lavas have become lighter and varioufly
.coloured. ?

As I vifited the, Stoves three feveral times,
and examined wijih great attention the lavas
that had fufiered alteration by the adtion 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 ihall
here briefly ilate.

It was an object equally important and
curious to afcertain to what 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 diminifhes, 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 pan of the decompofed \a.v&§
of the Monte delle Stufe are, externally^, of
a reddifh white ; and fome are of a black-
i£h 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 haematitic iron,
which beautifully cover the furface of thefe
lavas.

I detached a confiderable number of thefe
globules, and found that on trituration they
aifumed a red colour, which is the property
of the dark hematites. 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, interfe£ted with parallel
ftreaks of a reddilh blacky or lightly fhaded
with a yellowiih tinge.

Thefe lavas are foft, light, and compact ;

they

( 49 )

they adhere to the tongue, have the confid-
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 fradure is conchoidal ;
and that, when ftruck, they caufe a found
fimilar to that of fome kinds of petrofilex;
which has induced me to fufpedl they belong
to that fpecies of ftone : a fufpicion which is
confirmed by examining deeper within the
fradures ; 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 afpe<3:, and give a few iparks with fteel.
Still deeper we perceive without the lead
doubt that thefe lavas have a petrofiliceous
bafe, and contain a few fhoerls, 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 reddilh white. The ap-

VOt, in. E pearances

( so )

pearances in them are, eflentially, the fame;
The red colour in the internal parts infenii-
bly variifhes ; the grey by degrees fucceeds
the white, whieh, ftill deeper, acquires a
luftre, the lava at the fame time becoming
harder, and at length diftindly exhibiting
all the charaiSters cf the petrofilex.

One of thefe laTas, ftreaked with white
and a clear red like that of the peachy?;
flower, is fpotted on the fmrface 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
fofter, and even pulverable ;; though at the
depth of two feet it is hard, heavy, of a-
black- grey colour, evidently has a petrolili-
ceous bafe, and contains/ feltfpars which are
perfedly entire.

' Iii dderibing the variouily decompofed
lavas of Solfatara, we have feen that felt-
fpars are a kind of ftones which ftrongly
lefill the adion of acids. It frequently-
7 happens^'

{ 5» )

happens, that their bafe is completely
decompofed, while they are fcarcely in
the leaft changed. As, therefore, in the
prefent lava, the feltfpars 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 dough,
and almoft faponaceous; characters that
ufually accompany thefe decompofitions.

We muft not omit to notice a lava of the
breccia kind, the bafe of which is likewife
petrpiilex, and in which the adtion 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 fihall mafles of whitened
and pulverulent lava. Thefe, therefore,
have yielded m'ore to the decompofition
than the bafe that contains them. At a
greater depth we find them unaltered ; and
they are then only fragments of lava of a
horn-ftone bafe.

E 2 Though

( 50

Though many of the lavas of the Stoves
of Lipari have fufFered by the fulphureous*
acid vapours, there are feme that are entire-
ly unchanged. I fhall only defcribe one,
which is fo v^rell preferved 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 mafies from the
earth, it appears of a dark iron colour, has
an extremely compad grain, and a con-
choidal fradture. The fcales at the edges
are fharp and cutting, and give very lively
fparks with fleel. It is one of the heavieft
and 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 relift their ftrength,
but becaufe it was not expofed to their aC"
tion. The places^^ under -which the confla-
grations of a volcano burn, have numerous
apertures and fiflures through which iflue

fu'phureous

{ 53 )

fulphureous fumes ; and when lavas are
fituated around or within thefe, they will
be more or lefs afFeded by them. But in
the fame trads 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*-
vius, 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-
fucd 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 5 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 3 by

( 54 )

by a thick cloud of the fumes ufual there,
were already half decompofed, though they
were evidently parts of that current which,
but a few months before, had been difgorged
by the fide of the mountain. Laftly, ac-
cording to the different qualities of the
lavas, and as they may be compofed more
or lefs of calcareous, argillaceous, or martial
principles, all combinable with fulphureous
acids, a greater or lefs decompofition will
be produced.

The different degrees of decompofition
in lavas render them fometimes more, and
fometimes lefs fufceptible of fufion in the
furnace. The parts not decompofed will
fufe. A beginning decompofition renders
them flubborn, and, when it is complete,
they entirely refifl the fire. The caufe of
thefe differences appears to me fufficiently
Evident. The more earths are pure the
more they refill fufion. All thofe hitherto
known are infufible, except in very violent
fires. Their mixture facilitates their fulion,
as they thus become a reciprocal flux ; and

we

( ss )

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
exactly 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, a£ls 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 fuiibility 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 obftacle;

* To prevent any ambiguity, it may be proper tore-
peat what 1 have faid in Chap. II, that the pretended
tranfmutation of filex, or any other earth, into argil-
laceous earth, in the decornpofition of lavas, has no
€xiftence ; fince, in this cafe, that earth likewife is di-
jniniihed, from the caufes alleged above.

E 4 to

( 56 )

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

Thefe fulphates, which for the moft part
accompany lavas, prefent a pleafmg fpec-
tacle to the naturalift. Their colours are
infinitely varied. Thofe which are mofl
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 flrata or beds of different thicknefs,
fometimes more than a foot, and thefe flrata
are eafily detached from the lavas to which
they adhere.

The fecond fpecies is filamentous, having
either parallel or flellated filaments, in which
latter cafe the filaments form a kind of py-
ramids, which have their apices in one
6 common

(57 )

common centre, and their bafes at the 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 fhining plates, fomewhat elaftic, tranf»
parent, very foft, and forms the indeter-
minate cryftallization of fulphate of lime
called fpecular ftone j but this fpecies is
rare, and its cryftals are always very fmall.
In thefe cafes the determinate and primitive
cryftallization 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 leaft
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

( 58 )

with the lime, which is laid open by the
deftrudion of the adhefion of the confti-
tuent principles of the lavas, and varioufly
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 perfedly with experi-
ence, fmce, where the decompofition has
taken place, the lavas are incapable of
moving the magnetic needle, whtreas they
conflantly 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
produdions of the Stoves of Lipari, with
fome interefting remarks relative to feve-
ral different fpecies of zeolites, which I dif-
covered in their vicinity. I fhall defcribe
them feparately with their matrices.

Firfl: 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

fteeh

( 59 )

Heel. It fhews no indication of having
fufFered by the fulphureous acids. It is full
of fmall long cavities, all in one diredion,
and which probably were produced when
the lava was in a fluid flate. It is in thefe
cavities that this fpecies of zeolite is found.
At firft view it appears rather to be a ftalac-
tical calcedony, having the form of a clufter
of grapes. It is of a white pearl colour,
inclining to a light blue, and gives fome
fparks with fteel. It has a filiceous fradure,
and a degree of tranfparency. Three pro-
perties, however, efpecially charadierife it :
firft, that it forms a jelly with mineral acids;
fecondly, that it flafhes or blazes at the mo-
ment of fufion ; and, thirdly, that it bub-
bles, and as it w^ere boils, when in fufion:
and though neither of thefe chara^Sters 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 gtains 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

( 6o )

or three in breadth. The figure which I
have called cluftering, is the moft ufnal in
this fpecies of zeolite ; though fome arc
only oblong 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 ;
and feveral feconds were required for its
complete Uquefadion, even v/ith the aid of
oxygenous gas. It then changed into a
fnowy-whlte enamel, full of bubbles. It
has a lucid brightnefs when it begins to
melt, and boils and bubbles up when in
adual fuiion.

Second fpecies. This is found In fome
pieces of the former lava, but its charaders
are different from thofe of the preceding
fpecies. It coats over matiy of the cavities

before

• C 6i )

before mentioned with a thin cruft, thus
forming geodes, which, however, are not
cryftaliized internally. This zeolite, which
indines to a white colour, is more tranfpa-
rent than the other, and, from its hardnefs,
cuts glafs, almoft like rock cryftdl. The
mineral acids have no eff'edt 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 hun:ired grains of
this, pulverifed, were put into fix hundred
of diftilled boiling water. A foliition 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.

( 62 )

ivhite. In. the fradures we perceive that
they confift of a number of opake groups'
of fibres, ftriated, fiiky, and fhining, 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 m<ore than four lines in diameter,
perfedly 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 find zeolitic ftones with feverai
facets, but fo confufed that the precife con-
figuration of the cryftals cannot be diftin-
guifhed. On attentive examination, they
evidently appear to be formed of the 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 cryftaUized
more or lefs. Thefe zeolitic ftones always
have in the middle a fmall empty fpace,
where they are cryftaliized, forming a num-
ber of very minute geodes.

The

( 63 )

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

This zeolite, foon after it has been pus
into acids, attaches to the fides of the con-
taining veiTel in the form of a cruft, which
cruft prefently refolves itfelf into a tranfpa-
rent tremulous jelly, fi milar to that of hs^tC-
horn*

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

agree.

- ( 64 )

agree. This lava" contains a multitude of
zeolitic globules, from half a line to an inch
in diameter. On breaking them, a vacuity
is found within them, thus forming geodes
of a cryftaliization more or lefs perfed:.
Wherever the zeolitic fubftance has been too
confined in the cavity of the lava, the cryf-
taliization is extremely imperfed:, in con-
fequcnce of the prifms being half-formed
and cdnfufedly intermingled ; but where that
fubftance Had a larger fpace to develop it-
felf in, 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-
tindt conformation. Every prifm has there-^
fore four faces diflindly 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-
tranfparent j but others have a tranfparency
almoft equal to that of quartzofe cryflals.

A fmgle

( 6s )

A fingle 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 fufion is iimilar to that of the
zeolite of the third fpecies. A fimilar jelly
is likewife produced from it, and with 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 confidence : they both merit
to be diftindly defcribed. The firft fpecies
confifts of a great number of fmall fpheres,
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. III. 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 are 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 lengthwife. 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 naturalin:s. It coniifts of minute cry-
ftaJs, extremely clear and bright, which,
having facets in every part, vividlyrefledl 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 wiQied ; 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 ifoIaLed cryftals are extremely rare ;
the greater number being aggregated^ that
F 2 is.

( 68 )

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

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

This difference is ftili more confirmed by
the adion of fire and acids. The latter do
not ad, at leaft fenfibly, on the fixth fpecies,

though

I 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 the fifth,
which require a fire of much longer con-
tinuance for their complete liquefadion;
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 moft ex-
cellent for forming a gelatinous body, I
certainly obtained from it, very readily, an
extremely beautiful jelly ; but not in the
lead luperior to that produced by the thir4
F 3 and

( 70 )
and fourth fpecies. This foreign zeoHte Is
very white, and forms a group of fmall co-
nical bundles, clofely conglutinated, and in-
terfering 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 naturalifts, we fhall
find that the zeolites of Lipari have a great
refemblance to thofe of other countries ; and
it may be obferved that the firft fpecies is
very fimilar to that of the ifland of Ferro,
which Born has defcribed in his Lithophy-
lac'ium^ and which he has compared to the
flaladical calcedony.

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

mieu

<: 7' )

jnieu 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 eflentially
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
leaft, 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 affects
that form where its cryftallizations meet
with no obftacles. According to circum-
flances it is more or lefs modified ; and the
tetrahedral prifms of the fourth or fifth
ipecies are probably one of thefe modifica-
tions. The firft and fecond are amorphous j
F 4 but

( 7i )

but in the third we difcern a beginning cry-
ilaliization. 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 cryflals,
but thofe of the ifles of the Cyclops, which
have furniftied a glafs equal to this.

No mineralogill; is ignorant that Cronftedt
was the firft who diflinguifhed this flone
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 difTolved it into a gela-
tinous^

( 73 )

tinous body : and this flow diflblution, 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 fhewa that more than
one are not, in any manner, afFeded by
acids, even when highly concentrated. From
among fix fpecies of the zeolites of Lipari,
we have feen that the third and fourth pre-
fently form, with acids, a tranfparent gela-
tinous body ; which is lefs completely cha-
raderized 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 Bergraann, 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 was.

( 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 diflblve the union of the
Gonftituent principles of the zeolite.

The gelatinous diffolution of the zeolite
is neither a quality found in every fpecies,
nor is it peculiar to it, fince experience has
ihewn 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 produ<St:, induced me to
311 ake an experiment, of which I fliall here
give the refult.

The colourlefs garnets of Vefuvius con-
tain,

( 75 )

tain, according to Bergmann, 55 parts of
filex, 39 of alumine, and 6 of lime. Asj
therefore, I had collected 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
poffefs, 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 fofcened 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 diflblution was produ-
ced in the garnets by the alterations they
had fuffered j in confequence of which the
nitric acid, penetrating their internal parts,
had aded on them as it ads in many zeolites.

It

( 76 )

It has been believed that zeolites apper«
tain exclufi vely to volcanized countries, fmce
they 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
©f volcanos do not derive their origin from
fire, but are adventitious to thofe places;
sot that they were pre-exiftent to the vol-
canic eruptions, and taken up by, and in-
corporated with, the currents of lava, as a
celebrated volcaiiifl has fuppofed. They
werej no doubt, generated after the extinc-
tion of the confiagrations ; when their con-
Hitoent parts being depofited by water in
the cavities of the lava, and there combin-
ing by affinity, formed thefe flony fub-
HaoceSj according to circumflances, fome-
times amorphous, and fometimes cryflal-
lized ; In the fame manner that we have

fuppofedj

( 77 )

fuppofed, and, indeed, proved, the beautiful
quartzofe ftones to be formed in certaia
lavas on the fliores 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, with the following enquiry-
concerning an hypothefis adopted by M«
Dolomieu.

That naturalift was of opinion that the
zeolites of volcanized countries are only
found in thofe fituations which have beea
covered by the waters of the fea; and the
arguments he adduces to prove this, appear
to me fufficlently convincing with refpe^
to the multiform zeolites obferved by him.
But what fhall we fay of thofe we have now
defcribed ? I certainly did not neglei3: to
make the moft accurate refearches on the
fpot. It has been already faid that thefe

( 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 impreffions 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-
fiiells are found. The fame may, in like
manner, be obferved of the Vicentine vol-
canic mountains, which afford beautiful zeo-
lites, and alfo copious {lores of marine re-
mains. It is, however, certain that neither
Lipari, nor any of the Eoiian ifles, prefent
us with any vefllges of fea animals or plants.
1 do not mean to fay that this is a phyfical

demonflration
2

( 79 )

Jemonftration that tbefe 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 W'hich are not wanting in countries
that, at various epochs, have fuffered the
a£tion of fire ; I Ihall 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 refped: 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
lefs abundant in them, and the numbers of
them found in fome provinces of Sweden,
which have never been fubje(5ted 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 frefh water ; of which an ob-
fervation by Bergmann may furnifh an ex-
ample.

(80 }

ample. He has remarked that a fprmg of
warm water at Laiigarnes, in Iceland, when
it ifllies 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 fa<Sb
he fatisfa(SoriIy explains as follows : " While
the water is very warm, it holds the zeolitic
matter in difTolution ; but, afterwards, be-
coming cold, can no longer fupport it, fo
that it precipitates and forms this ftaladical
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 fires, diflblves the zeolitic fub-
ilances, which it afterwards depofits within
the lava, where they cryflallize, or remain
amorphous, according to circumftances.

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

* Opufc. Vol. III.

reached.

( 8i )

reached, 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 fc-
veral warm fprings, which fupply the Baths
of Lipari, of equal antiquity with the Stoves,
but, like them, now almofl forfaken ; and,
proceeding in the fame diredion, 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-
nifhed to find there is any volcanized coun-
try in Europe, in which the fulphureous
vapours, iffuing from fubterranean confla-
grations, have adted through fuch an exten-
five fpace. Thofe of Solfatara di Pozzuolo,
which have whitened its crater, and which

VOL. III. G are

( 82 )
are mentioned with a degree of wonder by
every writer on that volcano, are certainly
inconfiderabie indeed, with refped; to their
extent, when compared to thefe. Yet of all
the fulphureous exhalations wliich muft
have fpread themfelves fo widely over the
ifland, not one now remains in adtion, ex-
cept a few very thin fumes that rife frona
the ground near the Stoves.

I vifited the Stoves three times : the tw©>
firfl 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, whence
I proceeded to the high mountain of San
Angelo. We have already (ecn that Campo
Bianco and the Monte della Caftagna are
two mountains formed entirely of pumices
and glaifes, that is to fay, of vitrified fub-
flances * : but how extenfive muft be the
roots of thefe fubflances ! The declivity o£
the Monte delle Stufe, and its ample plain
covered with tufa, form, as has been ob-
* See Chap. XV.
1 fervedj

( S3 )

ferved, a bed of pumices, mixed with a
great quantity of glaffes and enamels. At
about the diftance of a quarter of a mile
from the Stoves, towards Campo Bianco,
the tufa difappears, 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 glafles.
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,
fuggeft to the reader the fame idea which
arofe in my mind when I firft 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 necefTary for the
G 2 produdion

{ 84 )

produdion of this great accumulation of
vitreous bodies by fubterranean tires. It is
certain that the produdion of pumices,
enamels, and glafles requires a greater heat
than the fimple fufion of lavas, when thefe
fubftances 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 ftones
from which thefe vitrified mountains have
been produced. The greater part are felt-
fpars, and petrofilex, with feme fmall quan-
tities of horn-ftone. As to the latter, it has
already been (hewn that it eafily vitrifies ia
a glafs furnace with n-o very vehement fire;
in which, likewife, many petrofilices and
fome feltfpars are vitrifiable *. It has alfo
been feen that the glafl^es, pumices, and
enamels of 'Lipari are all completely re-
fufed in the furnace. It appears to me,
likewife, that we have pofitive proofs that
tlie volcanic fire was lefs violent than that
of the furnace, in the fubftances, as well

* See Chap. V. and Chap. XI.

crjftallized

( 85 )

crvftalHzed as amorphous, v;hich, without
having fuffered the lead fufion, are found
incorporated in the pumices, glaffes, and
enamels of Lipari, and which may be per-
fectly liquefied in the furnace.

It cannot, however, be denied that the
generative fires of Lipari mufl, 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-
terefling and inflruCtive accounts relative to
the (late of the conflagrations which in, and
prior to, their times had been obferved in
Stromboli and Vulcano; and we have made
ufc of them when treating of thofe two
iflands. But we 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 relped; to
thefe antiquity is totally filent ; and we can
G 3 only

( 86 )

only infer that the volcanizatidn of thefc
two iflands was known to the ancients, from
a pafTage in Diodorus, who informs us, that
all the Eolian ifles were fubje<3: to great
eruptions of fire, and that their craters and
mouths were ftill vifible in his time ^''.
With refpedit 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; fince we learn frora
Homer that, after the taking of Troy,
Ulyfles landed there, and was treated with
the utmoft urbanity and courtefy by king
Eolus during a whole month, which he
continued there f 5 and though we allow to

ii}V K^aTtj^sg bi ysycVvi^EVOi km ta Tondla fiBX>?^ "^^ ^'"' ^'f
(pavspa. Lib. V.

•J- AioMw S"'£j VYia-ov a(pMo^i&'i evfla '^^va.izv
AioXog 'iTTTTOTaSVij, ^tXog adavaroiffi Qsoiai,
n^arn £v vwco. Horn. OdyfT. Lib. X.

Kat jW£v Tuv iKoixsaQiz tto'mv uai ^xfiara Ka'ha.

Ixiov, A^ysiwv T£ v£«j, Hai vorov A%a!ia)v. Ibid.

the

{ 87 )

the poet the ufual licence of poetry, it is {lill
moft certain that he could not have named
this illand, and the city it contained, unlefs
they exifted at the time he wrote his poem,
fince which nearly three thoufand years
have now eiapfed. But if we confult other
ancient and credible writers, we fhall find
that before Eolns, Liparus reigned in this
ifland, which from him took its name,
being before called Mehgonls^ or, according
to others, Mdigunis,

Another obfervation, likewife, here natu-
rally prefents itfelf. An ifland formed by
depofitions, and the fubfequent retiring of
waters, may, in a fhort time, be cultivated
and inhabited ; but it is not fo with one that
is produced by fubterraneous eruptions,
where the decompofition of volcanized mat-
ters is neceflary; that is to fay, a far longer
time. If, therefore, Lipari had inhabitants
and cities, and was a cultivated country
before the defl:rudion of Troy; it is evident
that it mufl: have exifted 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 beet^
preferved of it, as well as of thofe of
Stromboli and Vulcano. Ariftotle, indeedj
mentions the fires burning in Lipari, but
adds they were only vifible 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 glaffes ; though it is
evident, from what has been faid above, that
thefe bodies muft have exifted above three
thoufand years. We hence perceive what

* Kai TO BV in AiTta^a S'e Ttv^ (pavt^ov nai ipXayuoE?^ ou
fitv r,us§ag, (xTs^a xvkIo^ fiovov HaiBuSai >.sytTai.

In Mirandls,

an

( 89 )

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

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

C B A P.

( 9^ )

CHAP. XVIL

FELICUDA.

Two hays in this ijland capable of receiving
fmall vejfels — The produEis found 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 thefe lavas- — Enquiries relative
to its origin — Curious alternation of f rat as
of tufa and lava — Other prifmatic lavas
along the fhore—Ohfervations relative to
ihetn — Kxcurfon into the interior part of
the if and — A mountain^ near the ccfitre^
higher than the reft^ on ivhich is difcover-i
able the crater of an ancient volcano^ to
which^ probably, Felicuda oives its origin
■ — ConjeBures that another fmaller volcano
exiftedat thefumtnit of a loiioer mountain —
No other perceivable figns of volcanic
mouths throughout the whole if and —
^alities of the lavas forming the iiite-

rior

( 9^ )

rkr part of Felicuda — Glajfes, pumices^
tiifas^ and pu%%Qlanas fcattered over the
ijland — Pu%zolanas and pumices employed
by the inhabitants of Felicuda in building —
The fubjlances of which the if and is com-
pofed entirely volcanic^ except a piece of
granite^ ivhich appears to be natural — ■
RefleEtions on this rock,

\X yet remains to fpeak of Felicuda and
Alicuda, the two extreme illands of thofe
of Lipari towards the weft ; and I fhall 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,
1 fet fail from Lipari for Felicuda, diftant
from the former ifland tvsrenty- three miles,

and

( 9? )

and arrived there in four hours. This
ifland is not provided with a port; but it has
two bays, one on the fouth, and the other
on the nor th^eaft fide, fufficient for the re-
ception of fmaii veiTels, and fo fituated, that
though the wind fhould render the entrance
into one of them difficult, it will be eafy to
get into the other : both of them j^ire like-
wife fufficiently flieltered by a mountain.

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

Being thus fully convinced of the ancient

exiftence

( 93 )

cxlftence of fire in this iiland, 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 iflands,

Felicuda is nine miles in circumference,
I began the circuit of it by examining the
lavas that border the fmall bay which I
entered. Thefe have for their bafe the
fekfpar, which is of a fcaly confiftence, a
light grey colour, not very compact, hut
giving a few fparks with fteel and attracting
the magnetic needle. Within its fubftance
are included needles of black and fibrous
fhoerl, and fmall pieces of feltfpar, which
are eaiily diftingulQiable from the bafe by
their whitenefs, femltranfparence and luilre.
A part of the fhores of the bay are com-
pofed of this lava with deep fiflTures running
lengthwife, as we fee in many other lavas.
A number of round vacuities are likev/ife
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 a€tion of elaftic gafeous fub-

♦ fcances.

( 94 )

fiances, tvhen the lava was in a ftate bf
fufion, than to carrofions produced by the
influence of the atmofphere or any external
ajient. It is certain that the air of the fea
will greatly corrode many foffil fubftances
iituated in its vicinity J and I have witneiTed
extraordinary effeds from its adion on
many low rocks, on the (hore 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 mod
complete examples of fuch eiTeds. it is
fituated in the midfl: of fait lakes; and its
porticos and edifices are fo 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 fliort flay which I made
there in Odober 1792. The fea air, how-
ever, does not a<5tthus on every foffil fubftance

indif-

i 9S )

indifferently, but, with refped to ftones,
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 like wife
obferve that volcanic ftony fubftances 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 muil be
attributed to the action 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 obfervatlons, I
left the bay, and began to coafl: the ifiand
towards the left, on the northern fide. I
had fcarcely proceeded one hundred and
fifty paces when I met with a rock of lava,
about thirty feet high, and equally broad,
rifing almoft perpendicularly from the water.

This

( g6 )

This rock prefented a novelty I had not be-^
fore obferved in the Eolian ifles. This was a
Bumber of prifms into which the lava divided
before it plunged into the fea. The im-
portance of this object 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, fomewhat 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 water, of which I had
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 leffer waves of

the

( 97 )
the fea, and thus enable myfelf to perceive
fubaqueous bodies at a certain depth as cir-
cumltances 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-done of the black colour of iron,
and fo compad that the fmalleft bubble is
not perceivable in it; it muft, therefore, be
clalTed among the heavy lavas. The edges
of the thinneft flakes of it are tranfparent,
and give fparks with fteel. Its fragments
are amorphous, and receive a polifh, but
without luftre. It attrads the magnetic
needle at about the diftance of three lines.
The powder of this lava is cineritious, and
impalpable, and attaches to the finger. In

VOL. III. H it

( 98 )'

it arc contained various grains of amorphom
feltfpar, 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 refradory. 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 illand, which continues to
have a fteep defcent into the fea, offers only
common lavas, except one fpecies which
has fome rude appearance of prifms, that
afTume a more diftind; 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 //
Perdato^ 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 diftance of fifty paces farther, a
fpacious cavern opens in the lava of the
fhore ; an object 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 vv^as once
the retreat of fome phoca or feal, as in the
Lipari iflands, and many other places, the
phocce 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 furprifed by a ftorm may there find
ihelter.

H 2 Some

( 100 )

Some may perbaps willi to enquire, wlie-
ther 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 diflin-
guifhed by the following charaders.

Its bafe is fhoerl in the mafs ; it is mo-
derately porous, and therefore rather light 5
but gives fparks with fteel. It is unequal
in the fractures, has a fomewhat argillaceous
odour, and attracts the magnetic needle at
the diftance of half a line. It is of a grey
colour; but interfperred with white, fliin-
ing, rhomboidal 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 diminiftiing or deftroying, rather
increafes its magnetifm.

This

{ loi )

This lava, which forms the large cavern,
defcends almoft perpendicularly into the
fea, and there aflumes 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 we 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

( 102 )

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 precipice which defcends
into the Tea, the furtace of which is covered
with a tufaceous foil, refting on a bed of
lava, above another of tufa, and fo fuc-
ceilively, that in a rent made in the pre-
cipice by the waters we may number eleven
llrata or beds of tufa, and as many of inter-
pofed lava. It appears, therefore, that the
fire and water, by their repeated action,
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, fhoerls and feltfp.irs,.
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 )

iines, and the enamel into which it is
changed in the furnace has the opacity and
blacknefs of pitch, and its magaetifm is
greater than that of the lava before fufion.

The beds of tufa, likewife, do not eflen-
tlally differ from each other. They are an
ill-kneaded mixture of lumps of argillaceous
earth, more or lefs tinctured with yellow
oxyde of iron, which earth is eafily pulve-
rable. With it are mixed numerous, flioerls,
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 minutenefs, for fome of them are two
lines in length, but from their being fcarcely
ever found fmgle, almoft every one being a
group of aggregated fhoerls. When one,
however, is found fmgle and detached, it
appears to be an hexagonal prifm terminated
by two trihedral pyramids. They are black,
&ining in the recent fractures, and. are fome-
H4 what

( 104 )
what fibrous : in fine, they perfectly refem*
ble in their ftruc^ure the fhoerls incorporated
in lavas.

The tufa, after remaining two or three
hours in the furnace, aflumes a red colour,
and becomes hard 5 its magnetifm is like-
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
yellpwifh 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-^
je<Sts, excepting a long tra£t of prifmatic
lavas* fimilar to thofe I have already de^
fcribed.

I fliall conclude what I have to fay on

r thefe

( 105 )

tbefe pr'ifiRatic lavas, which occupy a con*
fiderable part of the • Ihore of the ifland,
with the following remarks :

Pirft. 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
fea.

Fifthly, Thefe prifmatic lavas have for
their bafe, either the horn-ilone or fhoerl in
the mafs.

I fliall

( io6 )

I (hall 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 fhore of the ifland, I 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 ftcep 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 the
central mountain, I perceived that it inclofed
a capacious hollow called FoIJa delle Feici
(the ditch of fern) becaufe it formerly was
overgrown with that plant; though when I
was there it had been all rooted up, with

the

( ic)7 )

the intention of fowmg corn the next
fpring. 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
erudations, 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

( io8 )

of which defcends to the fouth ; and, at
about halfway 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 Feli-
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 fpot, was more con-
firmed in my opinion. I found a hill,
about half as high 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 expreiTed myfelf with fome

doubt.

( 109 )

doubti I knovsT not of any throughout th^
whole ifland ; as I iliall not venture pofi-
tively to confider as fuch a number of cavi-
ties, hollows and caverns which we meet
with in various places, fuch appearances not
being fufficient to charadlerife a volcanic
mouth.

The principal lavas of the fhore of Feli-
cuda have already been defcribed fmgly : it
is nov7 neceflary 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 evidendy brilliant, without any appear-
ance of pores, and which gives fparks copi-
oufly Vv^ith fteel. The pieces into which it
breaks have no determinate form, do not
refufe a tolerable poliih, and move the mag-
netic

{ iia )

fietic needle at the diftance of a line and
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 opake
enamel.

This lava extremely refembles the prif-
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 afped:,
without pores, attaches flightlyto the infide
of the lip, and emits an argillaceous odour.
The llioerls it contains are rhomboidal, fcaly,
and of a violet colour.

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

5 The

( ni )

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

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

The feltfpars and quartzofe grains are
refra6;ory in the furnace; though their. bafe
is eafily fufible, and produces a fhiningj
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 i
which lavas form currents, that, from their
great antiquity, do not exhibit thofe tu-
mours, wavings, and inequalities, which are
obfervable ia recent lavas, or thofe of a mo»

derate

{ 112 )

derate age. The fame antiquity is, like^
wife, probably the reafon, why in Felicuda
we do not find fcorisE, 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 produdls of that iiland by the fulphu-
reous-acid exhalations. The contrary is to
be obferved of Felicuda, there not being a
fmgle lava which exhibits the leaf!: 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-
cuflomed myfelf in thefe refearches, I fhould
frequently have taken the fame lava for
others fpecifically different.

Having thus defcribed the different kinds

of

( "3 )

of lavas of this Ifland, It will now be proper
to proceed to treat of the other volcanic
fubftances It contains* 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 produ(!il:ive by cultivation*

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

I have already fald, that I had fcarcely
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 obfervatlon, and, finding I was

VOL. III. I in

( 1^4 )■

in fearch of this fubftance, brought me mote
of it than was neceffary, which they col--
leded in the fields where they worked. As
I was not, however, perfectly fatisfied with-
this firft obfervation, I diredied them to di^j
a deep trench in one of the fields which
moil abounded in fpecimens of this fub-
ftance, with a view to try if I could dif-
eover 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 forae of thefe vitreous pieces.
At a greater depth the virgin tufa appeared,
untouched by the ploughfhare, or any ruftic
inftrument. This tufa like wife furnifhed a
fimilar glafs, but always in detached pieces j
nor was any difference perceivable in the
nature of thefe produds, on continuing the
refearch to the bottom of the trench, where
the tufa was flill found.

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

that

( "5 )

that It was thrown out from the mouth of
the volcano in the fame ftate in which it is
now feen ; fmce it is only found in plates
or flakes, and with thofe points and iliarp
angles, thofe cutting edges and waving
llreaks, which we obferve in glafs, whether
volcanic or fadiiitious, when it has been
broken and divided into fragments by a
hammer, or other heavy body. We mull
therefore conclude, 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 tvv^o in thicknefs.
Many of them are not inferior in clearnefs
and brilliancy to the fined and brighteft
glafles of Li pari ; others are lefs tranfparent,
and of a cineritious, or grey, colour; while
others are almoft entirely opake; and thefe
approach nearer to the nature of enamels
than to that of glalTes. They are all, how-

1 % ever-

( ii6 }

ever, extremely compad-, and will readily
give fparks with flee), and cut common ar-
tificial glafs. Several of thefe pieces con^
tain vvitbin them fmall white particles, which
have been obferved and defcxibed in many
of the glafles of Lipari, whkh particles in-
dicate that the glafs containing theni is not
fo perfedly vitriiied 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-
tious colour, and, as appears from fome
analyfes w^hich I have made of it, is of a
petrofiliceous bafe.

This glafs, like other volcanic glaffes,
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 large maifes, but are al-
ways found in detached pieces, of rather a
fmall fize, the largeft rarely exceeding the
bignefs of the clofed hand. In general they

are

( 1^7 )
are more plentiful than the glafles, and
^mong the tufas of uacultivated places, it is
only neceflary to remove the furface to End
them by hundreds. During my flay at Fe-
licuda I refided in a pia^ce called La Valle
:della Chiefa (the Valley ^f the Church)^
This is a fmall plain, on the eaft fide of the
iiland, in which ftand the parfonage-houfe
and the church, two indliFerent buildings,
iuitable to the poverty of the country. This
place, as likewife a fpacious declivity to the
fouth, abounded with pumices, both on the
furface of the tufas, and below the furface^
rterever they were dug into.

Thefe pumices are of two kinds ; the
-one cellular, extremely friable, fibrous, and
which float on the water ; and the other
compad:, h«avy, without pores, and of a
fmooth fradure ; but which yet pollefs all
the true characters of pumice. Some are of
a reddifli colour, .others yellowifh, and
many aCh-grey. All are plentifully fur-
niihed v/ith extremely brilliant vitreous felt-
ipar-fcales.

I ^ In

( ii8 )

In my obfervations on the pumices of
Vulcano I have remarked, that inftead of
fwelling in the furnace, and being tranf«
formed into an ebullient produ£b, as is al-
moft always the cafe with glaffes and com-?
pad; enamels, they become of lefs bulk,
lofe their pores, if they had any before, -or,
at leaft, contrad, and therefore become
heavier. The prefent pumices do not dif-
fer in this refpedt from thofe of Vulcano ;
and the enamel which they produce in the
furnace has a black and fliining ground, in-
terfperfed with whitifh fpots, which are
feltfpars that, having loft their luftre an4
tranfparency, are become white. This ena-
mel puts the magnetic needle in motion at
the diftance of a full line, notwithftanding
that it had no fenfible efFedt on it when i4
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
4iredion which is ufually obfervable in

pumice^

< 1^9 )

|3Kmices that have flowed in the manner
■of lavas. The figure of the pores in pumices
that have flow^ed, is ufually more or lefs ob-
long ; whereas in the pumices of Feiicuda
(I mean the celhilar) the pores are almoft
always orbicular. We mufi: therefore con-
clude that they have been thrown out from
the mouths of volcanoes ; to which the glo-
bofeiigure .of many of them is perfectly
confonanto

I fhould efleem my account of the dif«
ferent productions of this ifland very de-
fedive, were I not to mention another
which ftill more confirms its volcanization :
I mean the puzzolana found here in feveral
places, and which, when carefully exa-
mined, is fpund to be a mixture of minute
fragments of pumices, tufas, and lavas. The
inhabitants of Feiicuda 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
^re ered:ed, for greater convenience, on the
1 4 fea-

( 120 )

fea-fhore ; and at the end of forty hours ai^
excellent lime is produced. One-third of
this and two-thirds of puzzolana, mixed
together with water, form a cement whicl^
unites and binds the pieces of lava here
ufed inftead of bricks and flones ; and to
give, as they affirm, a greater ftrength an4
folidity to the cement, they mix with it
pounded pumice of their own country.

Lavas are ufed as materials for the build-
ing of houfes, not only by the inhabitants
of Felicuda, but by thofe of all the other
Eolian ifles, each ufing thofe of their own
jflatid ; and it is the practice, not only m
the country but even in cities, to build vvdth
fuch flones as the environs afford, efpecially
when they are mountainous. I therefore,
wherever I wen^, conftantly examined the
materials of which the villages, towns, and
cities through which I pafled were built ;
which frequently alTorded rne a light an4
dire6.ion in my enquiries relative to the foA
fil fubftances of thofe countries,

Oh

( 121 )

On reviewing the difFerent volcanic bodies
which I met with at Felicuda, we fhall find
tliat they confift of glaffes, pumices, tufas,
puzzolana, and lavas with a bafe of fhoerl,
feltfpar in the mafs, or horn-ftone. The ifland
at prefent exhibits no indication of fubter-
ranean lire, and even thofe figns which are
uncertain and equivocal are wanting; fuch,
for inftance, as v,rarm fprings.

In the various excurlions I made, I was
particularly attentive to obferve if by acci-
dent I Ihould meet with any body not vol-
canized i and found one only of this de-
fcription. This was a piece of detached gra-
nite, lying on the fhore near the Grotta del
Bove Marino. Its elements were of the moil
common kind ; mica, feltfpar, and quartz.
The mica was partly black, and partly
white and filvery ; both forming groups ia
which the black predominated. The quartz
was in fmall femi-tranfparent mafles, 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

i I2Z )

exceeded the two other principles, and thcrci
foremuftbeconfideredasthebafe of the ftone,
was in fmall maffes of unequal furface, lamel-
lar in the fradures, tranfparent in the angles,
and of a changeable milky whitenefs. Nei-
ther of the three principles has a determi^
Bate form of cryftallization. I think I fhall
not be miftaken if I aflert, that this granite
lias not fuffered the adion of the fire. Iri
fad, a continuance of a quarter of an hour
in the furnace produced in it fo great an
alteration, that every part of it was fenfibly
changed. The mica became pulverable, the
quartz extremely friable and full of cracks,
and, iofmg its tranfparency and vitreous
brilliancy, became entirely white. The felt-
fpar, likewife, contra£led a confiderable fri-
ability ; Iofmg 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 ftone
into fmall pieces ; though before it would
only ftrikeofF, at moft, a Tingle fragment.
When expofed to the furnace for feveral
days fucceffively, the (|uartz and mica did

( 123 )

pot fufe ; and the feltfpar only exhibited, at
the angles, a beginning of fufion, which
made it appear as it were undluous. This
experiment is perfedly agreeable to many
others which I made in the furnace on the
granites treated of in Chap. XII. We muft
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 ia
the interior part of the ifland, 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
from Capo Melazzo in Sicily, or that vici-
nity, which is only fifty-four miles diftant
from Felicuda, and where immenfe mafles
®f fimilar granite are found %

» See Chap, Xll.

CHAP,

( 124 )

CHAP. XVIIL

A L I C U D A.

Danger to which the author was expofed^ In
a tempeft^ on his pajfage fro?n Felicuda to
AUciida — Pumices and glajfes found in the
latter ijland — ILxamination of the coafi of
Alicuda — -Several rocks formed of detached
globes of lava — Enquiries relative to the
origin of thefe globes — Confirmation of the
ttncertainty of any opinions formed relative
to the greater or lefs antiquity of lavas^
from the more or lefs feifible decompofition
they may have undergone — Ifolated majfes
of porphyry^ which exhibit no figns of
having been attacked by volcanic fire—^
Lavas of another kind — Shoerls of a
greenifh blue colour contained in all thefe
lavas — The coafl of A-Hcuda more rugged
and threatening than that of any other
of the Eolian ifies — No inouth of any
ancient crater in the fides of the ifiand

{ 125 )

-—The af)peara?ic£ of a ttue a^ater found

only at the fiimmit — Lavas ht the ifiterlor

part ef the fland fmilar to thofe of the

foores — -Improbability that Fel'icuda and

Aiicuda once formed afingle conical momi'

taiuy the fide of which has been opened and

feparaied by the fea, as M. Dolomieii has

fuppofed — Reafons for believing that each

was originally a feparate if and — Thcfe

two ifands no longer manifefl atiy fgns of

adlual fre — Theflence of the ancients re^

lative to their fery eruptions^ a proof that

they mifi have long ceafed to burn.

N the 13th of October, at fun-rife, I left
Felicuda, in a fmail bark, with four rowers,
which was fleered by the parifh-prieft of
FeUcuda, who had the character cf a fkilful
feaman. We failed before a moderate eaft-
wind : the fky was clear, the fea fmooth,
and we flattered ourfelves we fhould fooii
reach the place of our deftination, as the
diftance between thefe two fmail iilands Is
not more than ten miles. But fcarcely were
we half way, when the wind began to in-

creafe

( 126 }

creafe fo that we were obliged to reef otif
fail, which it was dangerous to carry fuH ;
yet flill we nlade more way than before |
and the wind blowing with greater violence,
and driving us rapidly tOvvards Alicnda,
from which we were nov^r not far diftant,
endangered our being fhipwrecked on the
fliore. Bays or harbours are things unknown
in this illand, and our bark driving before
the wind, it was to be feared, might foon
dafh 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
very formidable to our little vefTel, which
they broke over from fide to fide, and from
ftern to prow, whirling it round v^ith their
violence; v/hile the danger of being wrecked
continually increafed by our approaching
the ifland, notwithftanding all the exertions

we

( '27 )

Ve could make with our oars to keep oiFIte
Our failors, however, did not entirely aban- '
don themlelves to defpair, but confulted
whether it would be lefs dangerous to yield
to the violence of the waves, and endeavour to
run the bark on ibme fand-bank joining to
the fhore; 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 haftiiy defcendlng from the emi-
nences of Alicuda, and approaching the
ihore, which they quickly reached ; when.
one of them called to us in a voice which
might be diftindly heard notwithftanding
the noife of the waves, advifing us not to
be terrified, but to endeavour to keep where
we were, and he v/ould exert his utmoft
eiForts to deliver us from the danger by
which we were threatened.

This perfon, as I afterwards found, was
the parilh-prieft of Alicuda, who perceiv-
ing, from a diftance, the fituation in which

we

( 128 )

"we were, Iiad baftened, with four of tfe
iHanden, to give us affiftance. He had
brought with him a ftrong pulley, whicb^
when fixed oil the fhofe, was to receive a
rope, by means of which the velTel might
be drawn upon the land* B ;t to effed: this^
it was neccfTary to form a kind of inclined
plane on the fhore, along which the boat
might be drawn ; which was foon done,
with the fpades and fhovels that had been
provided for the purpofe.

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

( 129 )

failbr drew it tight, and faftened it to the
prow of the bark* We now committed
ourfelves to the firft wave that rolled upon
the fliore ; and, the five iflanders pulling the
rope with all their force, we were drawn '
with the bark up the flielving declivity they
had made : but the wave on its return,
dafhing impetuoufly againfh 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 difappointment,
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
diffuaded by thefe iflanders, who aflured us
it was impoflible fo fmall and crazy a boat
as ours fhould long refift the violence of the
ftorm in the wide fea- ; but that it muft either
overfet, or bilge and fmk. They advifed

VOL. III. K us

( i3<> )

us rather to coaft the iiland towards the
north, where we might poffibly find fome
fmall inlet, where we might be lefs expofed
to the waves; promifing us that they would
proceed the fame way along the fhore, and
afford us every afliftance in their power.
This advice we followed, and, bearing up to
the north, without ilanding 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 without damage, and landed, with
the afliftance of the worthy prieft and the
pcrfons with him, towards whom I fhall feel
the warmeft fenfadons of gratitude while
life fhall remain. He treated us, when on
fhore, with the utmoft kindnefs and hoipi-
taiity ; and when I had prefented to him the
circular letter 1 had received from the Bifhop
of Lipari (in which I was warmly recom-
mended to the paridi-priefts of thofe iflands,
who were requeiled to furniih me with
every aiTiftance neceflary for my philofophi-
cal refearches during my ftay)5he redoubled

his

( ^31 )

his civility, offering to ferve me in every
manner in his power ; and his whole con-
dud fufficiently evinced the fmceritj^ of his
offers.

It was not yet iioon, by fome hours, when
we landed in Alicuda, but the fatigue I had
undergone prevented my having any incli-
nation to begin my feiearches that day; and
the following night I flept in the bark, which
had been drawn on fhore ; my deliverer
(for fo I may juftly call the good prieft of
this iiland) 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 iiland. 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

( 5^2 )

and 15th of Cdober), during which I fiiffi^
ciently gratified my curioiity, and acquired
a fatisfa£tory knowledge of the nature of the
ifland. The obfervation of the ancient Gre-
cian philofopher is well known, who having
been driven by a temped on the coaft of
Rhodes, and with great difficulty reached,
the land, feeing certain geometrical figm'e^
traced in the fands, immediately exclaimed :
J perceive the veJUges of men : I, in like
manner, the moment I fet foot on the Ihore
of Alicuda and furveyed it, might have
exclaimed : / perceive the vejliges of jire^
Thefe were the pumices, glafTes, and ena-
mels, which prefented themfelves to my
view on the fkirts and fides of Alicuda, and
v/hich it is urineceiFary particularly to de-
fcribe, fmce they entirely refemble thofe of
Felicuda, and are found like them mingled
with tufaceous fubilances.

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

preceding

( ^33 )

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

I fhall here, therefore, fpecify the princi-
pal produdls 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
n^t name the places where I found them,
fmce two of the inhabitants who accompa-
nied me were unable to affign any names
by which they were known ; the different
parts of the fhore of the ifland having in
fadt no fixed names : I fhall only indicate
their diftances from the place whence I fet
out.

At the diftance of forty paces from that
part of the ifland which fronts the eaft, we
begin to find, as we turn towards the north,
entire rocks, formed of globes of a blackifh
lava, with a petrofiiiceous bafe, which,
though porous, is heavy from the compad:-
jiefs of the fblid parts, which have a iittle
K 3 luflre,

( 134 )
luflre, are very hard, and in their fradures
afFed: the conchoidal figure j they move
the magnetic needle at the dillance of more
than a Une, and give fparks tolerably freely
with fteel. The petrofiliceous fubiiance
contains a few feltfpars, and a confiderable
number of fhoerls. Thefe globes of lava
are of various fizes, fome of them being a
foot in diameter. They are detached, and
are never found in ftrata, hut only in large
accumulated heaps.

To what caufe can we afcribe the divifioa
of this lava, and its conformation in thq
manner defcribed ? I at firft imagined that
its figure might be the confeqiience of the
agitation of the fea, when its waters reached
to a greater height ; as thefe accumulations
of globes are now fome poles above its level.
In fad:, in my maritime excurfions round
the oth^r Eolian ifles, and at Etna, I 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 w€ find ftones rounded in rivers.
In the courfe of this work I have adduced
feveral examples of this kind, even among
the glafles 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,
confiding in general of minute parts and
points, muft have been worn away by rub-
bing againft any obftacle. I obferved, befides^
that thefe globes, in many places, had a
ihiningand fcoriaceous appearance, extreme-
ly fimilar to that of the pieces of lava inceC-
fantly thrown out by the volcano of Strom-
boli. I am therefore rather of opinion that
they are pieces of lava that have been
thrown out from a volcano in Alicuda, and
taken a fpherical form in the air, from their
great foftnefs, as fimilar phenomena may be
J^ 4 pbferved

{ 1.36 )

obferved in the produdls of other 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, or
rather vitreous in the frafture, and full of
fhoerlaceous cryftallizations. Whoever has
feen lavas which have lately ifTued from the
mouth of a volcano, would imagine this of
extremely recent date. On the furface, it
preferves that fhining afpe(!il, 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 where that
metal is fabricated. I have in my poiTeflion
fome pieces of the lava which was thrown
from the higheft crater of Etna, in 1787,
which I colleded on the fpotj and have dej

fcrlbe4

( '37 )

ibrlbed elfewhere *. Thefe, with refped to
the frefhnefs of their appearance, are not
diftingullhable from the lava of which 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 conclafions relative
to the greater or lefs antiquity of lavas, de-
rived from the more or lefs fenfible degree
of decompofition which they manifeft.
Such conclufions may be well founded,
when the lavas are of the fame nature, and
affeded by the fame extrinfic circumflances ;
iince, 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 ihall remain for ages, perfectly

1 See Chap. VIII.

preferved.

. ( '38 )

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 fall 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 mailes 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
compact, and without pores, except a few
fuperficial 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 few moments by the nitric
acid, and diifolve with a firong efFervef-
cence. This porphyry, in its hardnefs, po-
lifh and luftre, is not inferior to the Egyp-
tian. Befides flioerls, it contains numerous

cubical

( ^39 )

cubical lamellar feltfparSj of a changeable
whitenefs.

When expofed to the furnace for a few
hours it becomes black, and after a longer
time fufe into a black, compad:, and very
fmooth enamel, which fets in motion the
magnetic needle, though it produced nofuch
efFed: when it was porphyry. The felt-
fpars remain entire.

In this part of my circuit round Alicuda
I 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
as 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
w^th a petrofiliceous 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
jremained untouched,

A little

( HQ )

A little beyond the plain abovemention^
cd appear fome tufas, which cover a long
and fleep declivity defcending into the fea,
and beyond the tufas we again meet with
lavas forming broad currents. Thefe lavas
have the horn- (lone for their bafe, and their
external charadteriftics are the following :

They are light, extremely porous, and
therefore eafily penetrable by w^ater ; 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, w^hich 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 felti'pars, 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 afFedted 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 impoffible 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, fo torn and
fhattered, and fo filled with accumulated
ruins by the devaftations of time and the
fea.

In fome places v,^e find a lava extending

for

( Ui )

for feveral hundred paces, which hds bee^
broken by the waves in flich a manner ag
to form a rock furrounded by the watcr^
abounding in craggy cHiFs and precipices of
a fearful height.

In others the lava defcends perpendicu-
larly from the moft elevated fummit of the
mountain, and buries itfelf in the water, fur^
rounded on the fides by projeding 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<fxive flony torrent. Even the
large falcons, which frequent the higheft
fummits of this illand, if they chance to
alight on thefe heaps of round, loofe ftone?,
will often, as I have myfelf feen, by moving

2 , one.

( H3 )

oiie, put others in motion, till bird and
ftones fall, all together, headlong into the
lea.

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 mid ft, however, of thefe
mifhapen 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 throughthefe
I took my way, when from time to time I
landed from my boat and went in fearch of
the lavas I have defcribed, and examined
them on the fpot. I was obliged, however,
to advance with the greateft caution, as to
have made a fmgle falfe ftep would have
been to have fallen headlong dovsrn a pre-
cipice. I could not but recollecfl the lines
of Dante, in which he defcribes the la-
borious

( 144 )

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

" E profequendo la folinga via
Fta le fchegge, e tra rocchi de lo fcoglid,
Lo pie fenza la man non fi fpedia."

«' And ftill along the folitary way,

*' Proceeding over rocks and precipices,

*' The foot vi'ithout 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-
jQiores of Alicuda on the fourteenth of Oc-
tober, I appropriated the next day to the
examination of the interior part of th&
ifland. I could, however, only make my re-
fearchcs in the part which fronts the eaft
and fouth-eaft ; the remainder being inac-
ceffible from the dreadful crags and preci-
pices already mentioned.

Wheo

{ HS )

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 vnlh. 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 fa<3:, we. perceive no
marks of the mouths of ancient volcanos in
the whole circuit of Alicuda ; either becaufe
they have never exlfted there, or becaufe all
traces of them have been effaced by time or
fome other deftrudive agent. I have dif-
covered the appearances of a true crater no
where but in the higheft part of the ifiand,
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 lead
where I could reach them without danger,

VOL. III. L in

( H^ )

in tlie fame manner that I did thofe which
form the bafe or fhore of it. I fhall not
defcrlbe them particularly, as it appears un-
necefTary, 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 vv^ith a
yellowifh and friable coating, originating
in a beginning decompofition. The deep
fradures vvhich v^e find in many parts of
them enabled me to perceive that they muft
have flowed at different periods, forming
beds or ilrata one above the other, as is
frequently obferved in other volcanized
countries.

M. Dolomleu was of opinion that " Fe-
*' licuda and Alicuda had once formed a
^* fmgle 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

( H7 )

into two parts, it is difficult to conceive that
no record or tradition ihoiild remain of this
Gonvuhive reparation. On the contrary, when
I attentively examine and confider thefe two
iiflands, they have every appearance of being
each a diftindt ifland, like Strombcli, Saline,
and the others. Both likewife have on their
higheft fummits the veftiges of their primi-
tive crater, that is, of that which by its
erudations has given birth to its refpeclive
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 prove that
each was a complete ifland in itfelf ; nor
can I doubt but the French naturalifl:, had
he vifited thefe iflands themfeives, would
have been of my opinion. He only viewed
them from the higheft part of SaUne, 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 2 to

' ( i4§ )

to be only five miles from Alicuda, thongb
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 poffeffion of the intermediate
fpace.

From the fummit of Saline he, likewife,
eftimated Alicuda to be only twenty miles
from Cefalu, on the coaft of Sicily ; and,
in fa<^, when I was on the fame eminence,
ihefe two places appeared to me to be very
near, and Felicuda feemed almoll 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 illulion takes place with refpedt
to any obje£t feen at a diftance, either by
land or water. Nothing happens more
frequently to the traveller than to find that

two

{ H9 )

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

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

Notwithftanding 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 conjectured
that fome remains flill exift in the internal
parts of Felicuda, from a warm fpring,
emitting the fmell of fulphur, which iiTues
from the northern fide of a rock, a little
above the level of the fea,

L z I fliall

( 150 )

I {hall 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 Ericufa {<i>oivfKav(Tct and
'EoLx.ova-a)i which are faid to have the follow-
ing derivation : Ariftotle, fpeaking of Phe-
nicufa, or Felicuda as it is at prefent called;^,
fays, " it received that name from its abound-
ing in palm-trees" — cpoivi^^ in the genitive
(poinxos^ being the name of that tree in
Greek *. Ericufa, or Alicuda, we are told
by the author of the epitome of Stephanus,
was fo named from the erica or heath, which
there grows plentifully f . Strabo, like-
wife, informs us that thefe two iliands de-
rive their names from plants J. At pre-
fent, however, though heath is not wanting
in Alicuda, Felicuda does not afford a lingle

* Ev fAia Tuv Atohs 's^potxayopivofASvav vrjcruv 'sr^vjSoj ti (paiTi

In Mirandis.
■\ l^.piKHffffa^ (xia ruv AioXa vno-av, aTro (puis «a^8,u£J'n.

^ Tuv h ^oiTTuv EfiKnaa (ABV Kat C'ciVJKSo-^f aTTO ruv furuu
3i£K7'proii9 Lib a VI.

pa!m«

( 151 )

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

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

L 4 CHAP.

{ ^5^ )

CHAP. XIX.

OBSERVATIONS WHICH HAVE AN IMME*
DIATE RELATION WITH THE VOLCA-

NI2ATI0N OF THE EOLIAN ISLES

ENQUIRIES RELATIVE TO THE ORIGIN
OF BASALTES.

Methods and injlruments proper to raife Jlony
bodies from the bottom of the fea furroiind-
ing the KoUaii ifes — The bottom of the
channels between Vulcano^ Ltpari^ arid Sa-^
line^ entirely volcanic — The fame ohferva^
ble of the roots of the Eolian ifes beloiM
the ivater— Gravel and volcanic find in
the channel that divides Panaria from
Lipari — The rocks in the 'middle of the
channels betvueen Saline cind Felicuda^ and
between Felicuda and AUciida^ analogous
to thofe of the fame ifands^ but., probably^
primordial — Dec'ifve proofs deduced from
thefe obfervations^ that thefoerls and cry f
iallized feltfpars bf the lavas have not-

heat

( 153 )

hsai takeji tip by them <whe7i hi a fluid
Jiate^ fior formed isolthin them at the thus
of their congelation — Coffrmation of thefe
proofs — ^he Eolia?i ijles placed in a direci
line from eaji to wefi — A fimilar direBion
obfervable in fome ijlands and volcanic
mountains ifi other countries — Not impro-
bable that all the eight Eolian ijles were
formed at the fame timcy and perhaps
'Dery fuddenly^ with refpeEl^ at leafl^ to
their flrfl rudiments — Explanation of the
caufe why iflaiids and burning mountains
are fometimes produced difpofed in a right
line — Materials of the Eolian ifles^for iht
mofl part, porphyritic — Analyfis made by
the author, proving that the red Egyptian
porphyries have not for their bafe the pe-
irofilex, but rather the hornflone— -En-
quiry whether the vitrifications found in
fuck prodigious quantities at Vulcano and
Lipari, ere found in fimilar quantities in
any other volcanic countries — Uncertainty
of this from the want of accurate miner a-r
logical defcripiions of the greater part of
^jplfanos — The accounts given of them

iifually

{ ^,54 )

■ufually general and ivonderful^ hut little
inJiniBtve — Volcanic glafs found in Ice-'
land^ but by no means in fujfficient quantities
to form mountains- — No notices of vitrifi-
cations in the volcanos of the ifands of
Ferro^ nor in thofe of Norivay and Lap-
land— hittle or no glafs in the volcanifzed
countries of Germany and Hungary — Nor
in the extinguifjed volcanos of France —
'I'he quantity of vitrifications at Vefuvius^
and feveral other parts of the Neapolitan
territory^ more cQ?ifiderable — Scarcely any
at Mount Etna, or the volcanic mountains
of Padua — A more extenfive tradi of pu-
mices found perhaps in no part of Europe
than 171 the ifiand of Santorine — This
ifiandy however^ affords no glafs — Great
fear city of vitrifications in the three other
quarters of the globe — Conch fion : that
Vulcano and Lipari offer a greater abund-
ance f g^^^ff(^^ than any other volcani%ed
part of the ^lijorld ; but that Sa?itorif2e ex-
ceeds thtm in the quantity of pumices — ■
Enquiries relative to this fear city of vitri-
ations in volcanos^ whether burning or

extinSi

( '5.- )

exti?iB — // feems to prQ(;ced lefs from the
quality of the Jlones aBed o?i by the vol-
caii'ic fire^ than from the inefficacy of that
agent to produce vltr'if cation — A fuccef-
Jively flroTiger degree of heat reqiiifte for
a fione to pafs from the fate of lava into
pumice y and from that of pumice itito per'
feEt glafs — Elucidation of the caife *Lvhy
fome volcanos produce pumices, but not
glaffes — The formation of pumices hitherto
not attainable in our furnaces — Black the
natural colour of pumices, 'which arc ren-
dered white by external caufes.

Enquiries relative to bafaltes — Thefe origin-
nate in the humid way, 'when the word
bafalt is underfood in the fetife in zvhich
it was nfed by the ancients — The columnar
flones which^ from their prifmatic corifi-
guration, refemble the bafaltes of the an-
cients, originate according to circumftances
in the humid or the dry way. — F roofs of
their origin in the dry 'way in Vulcana
and Felicuda — Nature, in the jofjll king-^
dotn^ produces cryfials as well by the dry

4 way

{ 15^ }

<way as hy the- humid— This exemplified ht
the generation of hafaltes — An abufe of
analcgy to conclude from it one common
crigin of hafaltes-— When examined de^
iacbed^ they frequently bear no peculiar
charaEler of their origin^ which mi ft be
determined from local circumfances — Kn^
quiry "whether hafaltiform lavas have he-
come fuch hy a fudden condenfation ivithin
the fea — Proofs which focvj^ ffi i^<^i
many hafaltiform lavas have ajfiiimed this
fymmetrical cofifguration on coagulation in
the "waters of the fea ; fccondly, that in
ethers it has taken place only hy congelation
in the air ; thirdly^ that very numerous
lavas have proved refra&ory to this fgure^
both iscilthin the fea and in the air—The
property of afaming a prifmatic fgure ap--
pears y in many lavas^ not to depend on their
being of a particular fpeciesy nor on their
compa£inefs and folidity^ but on extrinfc
and adventitious circumfances — Thefe cir-
cunijlances indicated^ 'with an explanation
in what 77ianner^ according to their pre-
fcncc ar ahfence^ lavas frequently afume a

prifmatic

( ^5; )

■ prifmatk form i?i the air^ ^d)hih others
remain i?T€gular <wiiBm the fea,

i HE form, {ix^^ and ftrudure of the
Eolian 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 j
with the comparifon between the prefent
conflagrations and thofe of ancient times,
conftitute the principal objeds to be conli-
dered in writing the volcanic hiftory of
iiich 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 io.-^e.'n
iflands, and becaufe our objed was to write
the Lithology 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

« ( I5S ) '

tions which have a direct and immediate
relation to the deflagrations of the Eolian

ifles.

We have ah'eady obferved and defcrlbed
thefe iflands from the fummit to the bafe,
which buries itfelf in the waters of the
fea. But it was impoffible 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 fhould be exerted to ef-
fect it. It would be equally interefting and
inftrudiive to afcertain the nature of the
bottom in thofe tracts of fea v/hich fur-
round thefe iflands, and feparate them one
from the other. 1 fhall, therefore, here
relate what I obferved v/ith refpedt to this
fubjed, and defcribe the methods and inftru-
ments to vv^hich I had recourfe to make my
obfervations.

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

^7

( 159 )

by Donati *, furnidied with ftrong pincers,
fixed to one or more bars, which by means
of a rope may be clofed or opened at piea-
lure, 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 vv^hich
lifhermen ufe to envelop, and tear from the
rocks, coral and other fubaqueous bodies.
Thefe nets I eafily procured, as coral is
iifhed up on thefe coafts ; of which fifhery
I fhall treat further In a fubfequent part of
this work.

Employing, therefore, thefe two inftru-
ments, the following was the refult of my
obfervations, which Vv'ere not made on
pieces that lay detached on the bottom, but
on fuch as formed a continued whole with
it, as v/as evident from the recent appear-
ance of the fradures where they were brokea
off.

* Saggio fopra la Storia naturale del Mare Adrlatko
— ElTay on the Natural Hiftory of the Adriatic Se3„

la

( i6o ) ■

In the channels which divide Vulcanc^
from Lipari, and Lipari from Saline, the
bottom is entirely volcanic, and affords pro-
duds of the fame fpecies with the two
Ihores. The fame is obfervable of the foot
of the illands, which foot in fome fituations
defcends perpendicularly ; but in others has
a confiderable declivity, and thus enlarges
the circuit of the illand. The pieces of lava
which I was here able to detach, did not
differ from thofe of the fhore, which I have
already defcribed.

But at a greater diftance between ifland
and illand this was not the cafe. I made
my experiments in three different places.
The firft 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
teftaceous and cruftaceous 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 to be obfervedj were
volcanic.

The,

( i6i )

The fecond place in which I made thi^
fexperiment was between Saline and Felicu- '
da, and the third between Fellcuda and
Alicuda^ in both inftances, at the point of
greateft diftance, as nearly as the eye could
meafure, between the two iflands. In each
of thefe fituations, befides drawing up from
the bottom portions of the before-mentioned
cruft, I likewife obtained feveral ftony frag-
ments, w^hich, from the great force it re-
quired to feparate them, and the recent ap-
pearance of their fradlures, 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 Alicuda, and feven be-
tween Saline .and Felicuda. The bafe of
five * of them was a petrofilex almoft
opake, affording fparks with ft eel, compadl,
of a grain a little 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 t^'z;^ and feven.
T.

VOL. Ill, M of

( iSz }

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

Thefe eleven pieces, however, excited in
me a ftrong fufpicion that the rocks from
which they were detached had not been
expofed to the ad:ion of fire. The parti-
cles of the petrofilex in them were more
clofeiy united, had greater hardnefs, and a
more fdlceous appearance, than in the fame
ilone of thofe iflands which has been fub-
jeded to fufion. In like manner, the lavas
of a horn-ftone bafe ufualiy have fo me what
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-
ilru£tlve ivith regard to the origin and

formation

{ i63 )

formation of thefe iflands. We may con*=
dude from them : Firft, That the part of
the iflands which is buried under the waters
of the fea, has fufFered the a£lion 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
paflage to three diftindl mouths, gave birth
to three iflands, which conflagration, by
fubaltern and fuccefllve ramifications, and
ejections 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 Saline, nor
are any obfervable in Lipari, its whole efla-
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 fince

fince thofe parts, as far as the eye can per-
ceive, fhew no figns of the adion of fire.
Fourthly, That thefe three iflands, and per-
haps Hkewife Stromboli, are fituated in the
vicinity of analogous but primitive rocks.
The perfect refemblance of the fhoerls and
feltfpars in thefe rocks, both in thofe that
have fuffered 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 fatisfadion to confirm by
the prefent; and which become of the
greater importance, as I have lately read
that a naturalift of eminence inclines to be-
licTc that the fhoerls of lavas are formed
when the latter condenfe and become cold,
becaufe then the homogeneous molecules
feparate from the heterogeneous, and unite
by affinity in fmall cryftallized maffes.

This

{ i65 )

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 ihoerls, though many
were continued a long time in a ftate of
fufion, and afterwards fuifered quietly and
ilowly to cool and confolidate ; which 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 expofing them again to the furnace
detached from the lava.

The eleven pieces of primordial rock .
M 3 broken

( 1^6 )

broken from the bottom, exhibited in the
furnace the fame 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, Stromboli is the firft to the eaft,
and Alicuda the laft to the weft. This is
not the only inftance of volcanos having
produced iflands, or rather mountains, ar-
ranged in a redilinear 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 1 707, a new^ ifland was thrown up
by a fubmarine volcano, in the Archipelago,
near Santorine, 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,
U^nd, approaching each other, at length

united.

( '6? )

united, and, joining that which firft arofe
from the water, formed one fingle ifland*.

Another memorable inftance of this di*
redlion of volcanic mountains (for illands
are in fadt only mountains buried in part
under water) is the produdion of feven
lefTer mountains by the eruption of Vefu-
vius in 1 760 ; the account of the formation
of which, as it may tlirow 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 concuffions 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 railied from one of them ; the other
feven remaining entire, and incelTantly eject-
ing from their mouths vaft quantities of ig-

* Vallifneri Oper. fol. t. ii.

M 4 nited

( i68 )

nited fubftances, which falling almoft per^
pendicularly around the volcanos, produced,,
in the fhort fpace of ten days, feven fmaU
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 largeft,
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 erudations fhook 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 pfodu£tion of the Eolian iiles being
anterior to the records of hiftory, we know

not

( 1*9 )

liot whether this took place at one time, or
in diiFerent periods. The relation, however,
juft cited, of the origin of the feven Vefu-
vian mountains clearly proves the poffibility
pf their being produced at the fame time. It
alfo proves, that the whole eight might be
formed in no long fpace of time, with refped:
at leaft to their firft rudiments, it having
been feen that they 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 Vefuvian mountains above
defcribed, and of the Eolian ifles, have
formed a diredt 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 within the
earth, as well in foft fubftances as in the
more durable and folid ; within which clefts
ihould fubftances proper for the produdion

of

( I70 )

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

From the particular defcriptions of the
iflands of Lipari, we have feen that the
comhuftible 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 feltfpar. 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 rauft undoubtedly be buried at an im-
menk depth. If we would fimplify the
fads relative to the materials of all thefe
idands, we {hall find that they are for the
greater part porphyritic ; as are likewife
fome of thofe lubmarine tracts, apparently

not

( 171 )

not touched by the fire, and placed among
them ; as has been Ihewn 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 t. 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
rock. 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 which I have
fpoken of the eflential characters of porphyry,
t See Chap. XL

% Fromi

( 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 leaft 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
iHands.

The red Egyptian porphyries which I
analyfed are of two fpecies : the firft has
been defcribed at page n8 of Vol. II.:
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 fhoerls and feltfpars which they con-
tain.

Firji Species,

Silex, fomewhat reddiih, - 80
Alumlne - - ~ 7

Lime - - " " 3

Magnefia

( '73 )

Magneiia

. —

-

rs

Iron

Second Specks.

6

Silex

-

-

8i

Alumine

-

-

7i

Lime

„

-

4

Magnefia

-

-

2

Iron

-

-

4f

Befides the porphyritic lavas with which
the Eolian ifles abound, we have feen that
they contain great quantities of tufas ; and
thatStromboli is diflinguifhed 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
glafles which it contains. I cannot, indeed,
refled: on thofe enormous maffes 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, which

on

( 174 )

on the north and north-eafl fide abounds in
pumices, enamels, and glafies. The vitre"
Gus fubllances, therefore, of this iiland, and
thoie 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 impoffible to at-
tend to this ftupendous phenomenon with-
out feeling our curiofity excited to know
whether it be peculiar to thefe iflands, or
found iikewife in other volcanized countries.
But fatisfadlorily 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 extinguifhed,
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 myfel£
Of fuch a mineralogy, however, 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 amuf«
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 Ihores dry, and there inundating vaft
trads of land — fubterranean thunders, and
roarings in the air above — the fun difappear-
ing in thick darknefs at noon — whirlwinds
of fmoke, alhes, and flame, burfting from
the yawning gulf — burning Hones hurled
towards heaven, and falling in a fiery hall
— ^torrents and nvers of liquid iava, fulphur^
and bitumen, pouring down on the valleys
below, and carrying terror, defolatlon, and
death — illands, now fuddenly produced by
fubmarine erudtations, and now torn from
their foundations, and fwallowed up by

earthquakes thefe compofe the ufual de-

fcriptions of volcanps, which, though they
may not be ufelefs when the fads are faith-
fully ftated, and ^ot magnified by the ima•^

gination

( '76 )

gination of the narrator; yet they common^
Ij want one eflential requifite ; that is, li-
tliolpgical defcriptions 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 fcience, we may, with certainty, or, at
leaft, with the ftrongeft probability, , 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 eje<!:led 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-
tmdi or adive, it is certain, from the ac-
counts of travellers, that numerous glafTeS
are found, to which, the name of Icelandic
agate has improperly been given, only be-
caufe they have the luftre and beauty of
that (lone. The prefent eruptions of this
illand, likewife, not unfrequently contain
pum-ices ; but no perfon has ever alTerted
that there are entire mountains of thefe
ilones, or of glafles.

5 The

( »77 )

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
iflands, publilhedbyJacobfonDebes, 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 palling
to Germany and Hungary, we find fome
tradts of thefe countries that have like-
wife been fubje£ted 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

( 178 )

tial Memoir relative to the volcanos near
Old-Brifach,

Proceeding to a milder climate, and aj>-
proaching nearer to our own country, we
find that the extind: volcanos of France af-
ford no pumices or glaffes ; which aflertion
I can make on the authority of M. Faujas,
who has written fo well concerning them,
than which one more unqueftionable cannot
be adduced.

It is not the fame with Italy ; the coun-
try in which fire has principally extended
its empire. The Neapolitan territory pe-
culiarly abounds in pumices, enamels, and
glaffes, 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 ejeded
fimilar bodies ; but, with refped to Etna,
its fires rarely produce the ffighteft vitri-
fication,

« See. Chaps, IV, V,VL

Th§

( 179 )

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

The former, who vlfited 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 fubje6:,
fince it teaches us in what manner thefe
light ftones may be thrown up, immediately
by the fea, in volcanic eruptions. His ac-
count is as follows :

" About eighteen years ago, on a Sunday

" night, a violent noife began to be heard

" in the port of Santorine, which was like-

N 2 ** wife

( l8o )

** wife heard even to Chios, diHant more
" than two hundred miles, and was thought
'* to be occafioned by the Venetian fleet
" having engaged the Turks ; in confe-
** quence of which great numbers of people
" got upon the higheft places early in the
" morning, to be fpedators of the battle ;
" and I remember the Reverend Father
** Bernardo, a venerable man, perfectly de-
*' ferving credit, told me he was one among
*' the number of thofe who wxre fo de-
" ceived, imagining they heard a violent
" cannonade. They could however fee no-
*' thing. In fa£t, this noife was caufed by
" a fire kindled in the earth, under the har-
'' hour, the effe(ft of w^hich was, that from
'* the morning to the evening a vaft quan-
" tity of pumices rofe from the bottom of
" the fea, with fuch violence and noife as to
" referable repeated difcharges of cannon,
" and fo infeded 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

( iSi )

" been heard ; fince not only in this ifland,
'' but at Chios and Smyrna, all the filver
** became red, whether kept in cofFers or
'' in the pocket ; and the religious who re-
" fided 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 fo
*' blocked with them, that not even the
** fmalleft veffels could get out till a way
" was made for them by removing the
" pumices with long poles, and they are
*' ftill feen fcattered over the whole Medi-
** terranean, though in a fmall quantity *."

Tournefort, after having remarked from
Herodotus that Santorine was once called
KaAAi<r}j or " the mod beautiful ifland,'*
adds, that " its ancient inhabitants would

* Voyages dg M. 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 ftoncs, 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 ; whence it appears what a prodigious
accumulation of pumices there muft be in
this iiland 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 glalfes
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 would be fuperfluous to enumerate par-
ticularly, fuch an enumeration having al-

* Voyage du Levant.

ready

( i83 )

ready been made by Faujas, Buffbn and
others. I fliall only mention thofe which
afford produds that have relation to our
prefent fubjetS:,

"We read that the illand of Ternate, in
Afia, throws out a confiderable quantity of
pumices, as does, likevnfe, one of the nu-
merous volcanos of Kamfchatka.

As to thofe of Africa, we have but very
imperfed: accounts of them, with the fmgle
exception of the peak of TenerifFe, one of
the loftieft of volcanos i which, with refpedl
to its iituation, height, form, and crater,
and the hot fumes which iflue from it, has
been accurately defcribed by the Chevalier
Borda. But it were to be wiflied 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
" faad, black and red calcined ftones, pu-
" mices, and flints of different kinds *."

* Voyage en diverfes Parties de I'Europe.

N4 It

( i84 )

It admits of no doubt that the higheft
mouPitains of America, as Chimboraco, Col-
topaxi, Sangai, Pichencha, &c. form a chaia
of burni*ng volcanos, the largeft exifting ia
nature. We are indebted for the accounts
we have of them to M. Bouguer ; but thefe
are fuch as only tend ftrongly to excite
our curiofity without gratifying 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 glafTes, he does not make the flight-
eft mentior^ of them ; though it is well
known that the famous gallinaceous ftone,
which is univerf^lly 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 fron^
Quito.

'^ Acad, Royale des Sciences, 1744.

If

( i85 )

If we now confider thofe parts of thefe
imperfed accounts which relate to glafles
and pumices, we fhall find, with refped: to
the former, that the much greater part of
volcanos produce none, and that thofc
which do produce them, as in the Neapoli-
tan territory, Iceland, and Peru, are by no
means to be compared in this refped: with
Lipari and Vulcano. The fame may be
afTerted of Alicuda and Felicuda, the glafles
of which, though abundant in many parts
of thofe iflands, 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 Eolian iflands above mentioned.

If we confider the volcanos known to us
under one general point of view, we fliall
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-
fions, it is very rarely that they vitrify the
7 fubfl:ances

C 186 )

fubftances expofed to their fires. Refled-
ing on the immenfe quantities of vitrifica-
tions at Vulcano and Lipari, which are
almoft all derived from feltfpars and petro-
filex, the idea iuggefted itfelf to my 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
elfewhere. But this fuppofition does not
accord with fad: ; as we have feen in many
other volcanic trads, 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 flighteft appearance
of glafs. On the other hand we have
fliown, that, befides feltfpar and petrofilex,
many pumices have for their bafe the horn-
ftone and afbeftus, and many granite, as
M. Dolomieu has obferved. 1 am, there-
fore, of opinion that the caufe which has
produced them fhould rather be fought in
the volcanic fire, which rarely has fufficient
adivity to vitrify the ftones and rocks on

which

( 187 )

which It exerts its power ; though I grant
that the petrofilex and feltfpar are more
adapted to this vitrification than other
ftones. To produce a lava, a certain de-
gree of heat is neceffary j and a ilill 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 ftill 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 pafles immediately into perfesfit glafs,
, which muft be caufed by a fudden heat,
greater than that required to change it into
pumice. This theory fatisfadorily explains

why

( i88 )

why fome volcanos produce pumices, but
never glafs ; as may be remarked of Santo-
rine. Their fires are only fuiEciently
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 Phlegraean Fields, as alfo at
Vulcano, Lipari, Felicuda, and Alicuda,
glafTes are found mixed with lavas ; which
ftiews that the fire has aded unequally in
thofe places. It is to be remarked, at the
fame time, that the heat requifite for vitrifi-
cation is not of the mod violent kind, as I
have ihewa in Chap. XVI.

We muft however obferve, that as the
produdion of compad: lavas is a fecret
Tvhich Nature has hitherto referved to her-
felf ; fince we are unable to imitate them
with our common fires ; fo alfo are we
ignorant of the precife caufes of the forma-
tion of pumices. Among fome thoufands
of fufions which I have made in the fur-
nace.

( 'S9 )

nace, both of lavas and primordial rocks
and ftones, thofe likewife from which pu-
mices are mofl; frequently produced, as pe-
trofiUces and feltfpars, I never obtained a
produdl which could be faid to poflefs all
the charaderiftics of pumice. It has al-
ways been either a glafs, an enamel, or
fcoricC ; 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 charad:erizes
pumices ; fince, when I have ufed a more
moderate fire, the fubftances on which I
made my experiments have either not
melted, or been more or lefs vitrified.

I {hall conclude thefe obfervations on the

pumices

( 29^ )

pumices of Lipari with a remark relative
to theif colour. Except a few that are
dark, they are all white as fnow. Hence
the mountain of Lipari, v\^hich forms the
great magazine of thefe ftones, is called
Campo Bianco (the White Field) : but cer-
tainly there mull have been a time when
it Ihould have been denominated Campo
Nero (the Black Field) ; at leaft it is certain
that pumices when newly ejeded from
Yolcanos are of a black colour. This re-
mark, which has been omitted by almoft
all who have made obfervations on this
fubjedl, who content themfelves with faying
that this or the other volcano throws out
pumices, has been exprefsly made by Don
Ga^tano de Bottis in his " Hiilory of the
Conflagrations of Vefuvius *." He tells
us, the pumices ejected 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.

* Iftoria di varj Incendj del Vefuvlo.

Their

( 191 )

Their whitenefs was fubfequently acquired,
and probably was cauled by the impreffions
of the atmofphere.

Before I conclude thefe obfervatlons on
the Eolian ifles, I think it neceflary to fay
a few words on a fubjetS: which has a re-
lation to the productions of Vulcano and
Alicuda, and on which the opinions of
modern naturalifts are divided ; I mean the
bafaltiform iavas 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 within thefe few years
relative to the origin of bafaltes. To re-
peat all that has been written on the fubjeCt
would fill a volume ; but I am far from
purpofmg 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 )

witliout any very prolix argumentation.
Literary difputes 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 queflion. 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 ftones. It is now generally
known, becaufe it has been repeated by a
hundred writers, though perhaps by the
greater part without due confideration, that
the word bafaltes is ufed by Pliny and Stra-
bo to denominate an opake and folid llone,
of the hardnefs, and nearly of the colour,
of iron, commonly configurated in prifms,
and originally brought from Ethiopia ; of
which ftone the Egyptians made ftatues, far-
cophagi, mortars, and various utenfils. This
premifed, it remains to enquire whether
this ftone was of volcanic origin or not.

( 193 )

hy repaliiag 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 Volcanos are fo much indebted,
has difcovered, during his ftay at Roma,
an equivalent, in fome meafure, with re-
fpe£t to the folution of this queflion.
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, which have all the charaders
attributed to bafaltes, and likewife preferve
the name. Thefe he has lludied with the
greateft attention, and declares that the
ftone of which they are formed manifeds
no fign of the action of hre. Among
other Egyptian monuments, he obferved
fome of a green bafaltes, which change co-
lour, and affume a brown tinge, firhilar to
VOL. III. O that

( ^94 )

that of bronze, on being expofed to tlie
flighteft heat. All thofe that have beei3
burned have acquired this colour ; which
proves, as he very judicioufly obferves, 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 perfedtly 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
wider fenfe, and underftanding by it all
thofe columnar ftones which, by their prif-
matie 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 Seheibenberg,

* Rozier, torn, xxxvil. an. 1790.
f De Produclis Vulcanicis.

which

( 195 )

which are the efTed of a precipitation by
means of water ; and concludes that " all
bafaltes are formed in the humid way 'j^.'*

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

I fhall not repeat tvhat various Volcanifts
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 refpedt to the former
ifland, I have remarked, in Chap. XIlI,
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

* Rozier, torn* xxxviii. an. lypi*

O a defcribed

C 19^ )

dfefcribed the qualities and nature of thefe
prirmSi In Chap. XVII I 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 alTumed,
generally, by Werner and ether Germans,
•but that it is truly volcanic. It confe-
quently appears that Nature obtains the
ilime eifed by two different ways. In the
foffil kingdom, one of her grand operations
is cryftallization ; which, though it be moil
frequently effedted in the humid way, is
fometimes produced in the dry ; as we fee,
among other inllances, in iron, which Na-
ture cryftaUizes 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 inllances, of the cryflalliza-
tion of the fame metal by the action of fire.

* See Chap. XL

f And

( 197 )

And did other metals exift in the entrails
of volcanos, and the necefTary circumftances
concur to their cryftallization, it is indubi-
table that this may be efFeded by fire as
well as by water. Thus we fee that, by
taking certain precautions, metallic fub-
ftances affume a regular and fymmetrical
difpofition within the crucible. The fame
is true of bafaltes, the prifinatic configu-
ration of which, though not ftridly a cry^
ftalUzation, has the moft exa6: refemblance
to it. Obfervation, likewife, teaches us
that the fame combination of earths, ac-
cording to different circumftances, forms
prifmatlc bafaltes, fometimes in the humid,
and fometimes in the dry way. The ftone
called trapp, found in the mountains of
Sweden, is configurated in prifms, though
thofe mountains are of aqueous origin ; arjd
the horn-ftone, which is fo analogous to
the trapp, has the fame configuration at Fe-
licuda, notwithftanding it is a true lava.
In the fame ifland, likewife, other bafalti-
form lavas have for their bafe fhoerl in
THafs, and thofe of the crater of Yulcano,
0 3 the

( 198 )

the petrofilex ; which two flones, according
to the obfervations of M. Doloiiiieu, 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 a<ftion as we might at firfl: 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 1 have frequently feen the
mud of rivers, w^hen 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 contradtion that take place by the pri-
vation of the fire which held them in a
ftate of fluidity.

It appears to me, therefore, that the dif-

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, naturalifts would
make an impartial ufe of their own obferva-
tions and thofe of others. Some volcanifts,
perceiving that the generation of various
bafaltes is evidently igneous, have immedi-
ately inferred that all muft have the fame
origin. In confequence of this principle,
they have drawn lines or zones, in different
parts of the globe, indicative of extindt vol-
canos, which they have inferred from find-
ing bafaltes there ; and thus pourtrayed a
picSture of prodigious dimenfions, repre-
fenting the ruins caufed in the v/orld by
fubterranean conflagrations. Other natu-
raliits, on the contrary, being convinced
that certain bafaltes are the produce of
water, have affigned to all the fame origin.
From the fads 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 decifive
O 4 marks

( 200 )

marks of their origin. Local circumftances
alone can determine to which of the two
principles it is to be afcribed ; to difcover
which we mull attentively examine whether
the places where thefe figm'ed ilones 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 ;
in which cafe it will be neceiTary to re-
double our attention, and fix it on the fub-
flances 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-i-
ploying thefe means, we fhall be certain,
widiout fear of error, to elucidate and ad-
vance the enquiries relative to bafaltes, and
be enabled accurately to determine which
of them are to be afcribed to the action of
water, and which to that of fire.

But here a fecond queflion occurs, not
|efs interefling than the firft, relative to the

( 201 }

caufe why certain lavas, dlrFering from m-
numerable others, become baiaitiform; fmce,
if this configuration depended on conge-
lation, it muft be found in all lavas when
they had ceafed to flow. The firft vv^riter,
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 {ea^
by the fudclen condenfaiion which took
place on their flowing into it in a liquid
ftate J other fecondary circumflances, how-
ever, concurring, fach as a greater homo-
geneity, and a certain attradion of theii''
parts.

Of the fame opinion is M. Dolomieu ;
though he does not deny that even porous
lavas may fometimes, likewife, take the
form of prifms. The former of thefe opi-
nions is little lefs than hypothetic, while
the latter is fupported by facts too import-
ant to be curlbrily flated. M. Dolomieu
obferves that all the currents of the lavas of
ptna, the periods of which are preferv^d in

hiftory.

( 20Z )

liidory, have conilartly experienced two
effeds in their cong lation. 'Ihofe which
have cooled in the air, have divided, iu
confequence of the contradion theyh^ve fuf-
fered by the lofs of their caloric (heat), into
irregular maffes ; while all the others, which
have precipitated into the fea, have, on their
fudden congelation, contraded in a regular
form, and divided into prifmatic columns,
which form they have only taken in the
parts in contad: with the water of the fea. Of
this he met with evident proofs along the
ihore 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 quantity, yet in fomxC 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 Drifmatic lavas were cer-
tainly not the lad. While making the cir-
cuit of the Eolian iflands, of Etna and of
Ifchia, I conilantly obferved carefully the
conformation of the ftony currents which

fall

( 203 )

fall into the fea, I have remarked, when
treating of Ifchia, that this configuration is
frequently prifmatic, and that the prifnis
are conftantly formed in thofe 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
fitUdtion of thefe prifms clearly fliowing
that they were formed at the time of the
immerfion of the lava into the fea, which,
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 well as Felicudaj
prefents us with numerous currents and
rocks that defcend into the fea ; and they
are likewife found at Saline, Lipari, Strom-
boli, Panaria, Bafiluzzo, and Vulcano ;
but theie rocks and currents, which to-
gether extend over a fpace of more than
fixty miles, do not afford the flighteft indi-
cation of prifms.

As I went by fea from Meflina to Cota-

nia.

( 204 )

nia, and returned to Meffina from Catania^
I had an opportunity twice to examine, at
my leifure, that trad 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,
confifts of prifms more or lefs charaderized,
and fuch as they have been defcribed by
M. Dolomieu ; 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 iiffures and angular pieces, fuch
as are, generally, obfervable in all lavas,
which feparate more or lefs an tl^eijT cong^^
latioup

In my circuit hy fea round the fliores 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 diredions and angles fajl into

the

( ^^5 )
the iea : but I have already obferved, when
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-
tlci, have been much fpoken of. When I
made my obfervations 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 wei'e
" 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-
" pad: lava, with perpendicular and ex-
" tremely irregular fiUures, forming qua-

" drangular.

( 206 )

*^ drangular, and fometimes trapezoidal pU
** laftefs, which have been employed in
" building?. Similar fiffures 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 fuffet
on falling into the fea.

It may, perhaps, be objeded, 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 muft immediately perceive how little
folidity there is in this objedion. I admit
that the violence of the fea may, in fome

lavaSj

( 2o; )

lavas, have totally deftroyed thefe prifms 5
but that it can have had that efFedl 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 perfect, v^hile the
reft of thofe iflands have entirely loft theirs,
notvvithftanding they are all equally expofed
to the fliocks of the waves.

I cannot here omit another remark. It
is certain that more than one of thefe
iflands were not formed by one eruption,
but by fucceffive ejedions of lavas accu-
mulating on each other ; and in fome deep
lifTures, occafioned by the fea, this fucceffive
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 prifmatic,
the fame change muft have taken place,
alfo, in the former ; which being defended
jL from

( 20g )

from the injuries of the fea, by the extef^
nal ftrata, muft ftill preferve their prifmatic
configuration, of which, however^ no traces
remain. We muft, therefore,- eonclude
that innumerable lavas may fall into the
fea, without having their external appear*-
ance in the lead changed by the fuddea
congelation Vv^hich then takes place.

That the prifmatic configuration of lavas
is not always the efFed: of their immerfioa
in the waters of the fea, likewife appears
from many of them taking the fame form
in the air ; of which we have a diftio-
guiHied example in the crater of Vulcano,
Here, certainly, we cannot fuppofe any ia-r
tervention of the waters of the fea. Si-
milar obfervations have been made on
JVIount 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 vail crater, where
" there is certainly no probability of the
" fea ever having reached ; and I have

" frequently

( 209 )

" frequently found polyhedrons bafaltes
" perfedly charaderized in excavations
*' made by men in the centre of lavas,
" which have iflued from the fides of
" Mount Etna, in periods much poflerior
" to the retiring of the fea."

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

I fhall only remark, that I do not per-
ceive the abfolute neceflity of the fiflures
in this cafe ; fmce we frequently find lavas
with this configuration in perfe(5bly open
places ; as I have feeil 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-
edly, would have mentioned it.

VOL. Ill, P What

( 2IO )

What conclufion, then, ought we tode-'
duce from all thefe fads and obfervatlons ?

Firft : that many bafaltiform lavas have
affumed 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 fea
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 marlej the latter, in drying, divi 'e

into

( 211 )

into polyhedrous, pieces ; but when the
water pafled 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 eiie<fied differently.

It has already been faid, that feveral of
the prifmatic lavas of Felicuda have for
their bafe llioerl 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 fimilar fmoothnefs
is obfervable in fome of thofe of Mount
Etna, on the fhore between Meflina and
Catania, which have for their bafe the
horn-ftone ; though others extremely re-
fembling them, between Jaci Reale and
Catania, are formed in prifms.

Compadtnefs and folidity are, likewife,
not a necelTary 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 amcrpliouf
lavas on the fhores of feveral of the Eolian
iflatids are more compact than the prifmatic
lavas of Felicuda.

What then can be the intrinfic ch'cum-
ftance of the lava which 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,
fince it may be extrinfic 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 inftan-
taneous contraction of lavas.

The fafts which xve 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 fufficient,
with fonie requifite modifications ? Thefe
I will endeavour to fuggeii, illuftrating
my conjecture 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 fummlt 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 contraction have taken
place in fome lavas from the mere influence
of the atmofphere, though the lava w^as
not included in any cleft or fifTare r 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 ; fince a body
lofes its heat the fooner, the lefs-its thick-
nefs and denfity. This fudden contracSlioa
P 3 may

( 214 )

may alfo be produced by the circumftances
of the atmofphere ; as, fhould a ftrong
wind, of a very cold temperature, blow at
the time. The mehed lavas in our cru-
cibles will be found to give greater weight
to this latter conjed: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, and ufually irregu-
lar -J but, when they are immediately, in
the winter timej carried into the cold air,
the liiiiires, befides being deeper, will fre-
quently be difpofed in fuch a manner, as
to form fmall polyhedrous prifms, which
may eafily be detached from the reft of the
lava.

With refpei^: 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
ilrong degre-e of effervefcence and dilatation,
and that it muft be deeply penetrated with
the igneous fluid, otherwife the contradion

.necefTar?

( 215 )

necefTary to produce prifms cannot take
place. But many currents which defcend
from the fummit of burning mountains to
the fea, muft have loft their effervefcence
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 impelling gravity
of the lava, which frequently fails into the
fea perpendicularly.

Such is the hypothefis by which I would
explain the caufe why fome lavas have af-
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 fad:s be difcovered, pre-
ferable to mine, which I confider as only
conjectural, I fhall receive the communica-
tion of it v/lth fmcere gratitude, and adopt
k with pleafure.

P4 CHAP.

( 2l6 )

CHAP. XX.

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

Hxciirftoji inade to the Euganeati ^noiinta'ins^
by the author^ during the vacations of
1789, In order to compare the produBs of
the volcanos he had vfited with thofe of
the mountains of Padua — Dcfcription of
different fpecimens colledied by him in this
excurfion — Three kinds of lavas at Monte
Caflello — Erratic petrofiUces mingled with
them^ of uncertain origin — Lavas of Mon--
te del Donatio fo??ie vuith a petrofiUceous
bafe^ and others with a horn-fone — 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-r— Monte Ortone
abounds in prifmatic lavas ^ but fuch as are
lefs charaSlerifed in their configuration —
Lavas of Monte Merlo with a granitous

bafe

( 217 )

bafe — Black mica o?ie of the component
parts of this granite^ which has the pro-
perty of being attraEled like iron by the
magnet^ a property poffeffed likewife by the
other micas of the Euganean mountains —
The micas of the primitive grariites dejii-
tute of this propei'ty ^ hut capable of receiv-
ing it by the action offre — This important
facifurnifhes a clear proof of the ^volcani"
station of the Euganean moutitains — Nodo"
Jities of quartz contained i?i this granitom
lava^ probably produced by filtration pofe-
rior to ignition — The fame obfervable if
fome fjoerlaceous nodofities included in it-—
The fdoerls of the Euganean mountains aB
on the magnetic needle^ like thofe of other
volcanic coimtries, and in that differ from
thofe which are not volcanic — Calcareous
carbonates intermixed with the lavas of
the Euganean mountaiiis — Flints frequent-
ly found among thefe calcareous carbonates^
'which prefent the mojl fpecious appearance
of the change of lime into flex — Proof by
chemical analyfts^ that it is not neceffary to
have recourfe to any fuch change to explain

this

( 2i8 )

this appearance — Strata of globes near
T'eolo abounding in particles of pitch -Jlo7ic
■ — Veins of pitch-Jlone lavas atBajamonteand
Sieva— Groups of pumices enclofed in one
of thefe veins — Comparifon^ in the dry
•way^ of the no?2-volcanic pitch -f ones ivith
ike volcanic — Proof by the humid ivayy
that both are of the fame kind — EJJential
differences bet-ween the pitch f one lavas and
the volcanic glaffes — Volcanic produ&ions
of Schivanoja^ Monte Merlo^ Mafcabo^
T'remonte and Pendife, zvhich have been
fly led volcanic glafs by a living "writer,
hut 'which in reality can only be called
pitch-f one lavas ^ and but one of them ^ at the
iitmoji^ a vitreous lava — Mi/lake of this
author in having taken for volcanic glafs
fome pieces of glafs from the furnaces of
Murano, near Venice^ vohich he cafually
found in thofe mountains — Pemarks on
this accident^ vohi-ch fhould teach us to be
cautious in forming a judgment 'whether a
mountain be volcanic or not^ from fnding
a detached piece of glafs ^ or other produc-
tion of the f re j f nee it may be uncertain

whether

( 219 )

<whether that fire was volcanic or not — -
P ojfih lilt y of being equally deceived by pro-
duElio7is truly volcanic but erratic — Proof
of this from a circinnftance ivhich hap-
pened to the author — Little credit to be
given to accounts intended to prove the ex~
iftence of ancient volcanos — Neceffity that
fuch accou?its fhoiild be Uthologically de^
tailed — /;/ what manfier our judgments
relative to lavas may be frequently mif
taken — Volcanic rocks may have the mojl
fpecious appearances of lavas, though they
never formed currents — IVhen other proofs
are wanti7ig^ cellulofity the 7nofl certain hi-
dicatio7i that volcanic rocks have flowed in
a frcam — 'This cellulofity foimd i7i ma7iy
Euganean lavas — Si7igularity of the felt-
fpars of a lava near Rua, vohich have^
almof ally a portion of that lava for their
central nucleus — Lavas of Galzignano^
Pigozzo, Mo7ite NuovOy Monfelice^ and
Arqiia — -Singidar lava of Mo7ite Nuovo
co7itai7iing feltfpars be coin c earth ; and a7i''
other at Monfdice co7itai7iing pumices —
Lavas of Catajoy one of which for7ns co-
lumnar

( 220 )

lumnar prlfms — RefleSfions a7id corollaries
— 'The Kuganean inountains once were
iflands^ like tbofe of Pon%a^ the Eolian^
Santorine, ^c. — Their prodigious antiqui-
iy^ and vicitiity to civilized places^ two
caufes of the great changes they have un-
dergone— Their lavas analogous to thofe
of other volcanos^ in having rocks for their
bafe — Comparifon between the rocks of
other volcanos and thofe of the Euganean
mountains — Immenfe depth of thefe rocks^
•which would remain unknown to men
'were it not for volcanos — Three different
hafes in the Eugajiean rocks ^ deferving oh-
fervation : the feltfpar in the mafs^ the
volca?iized petroflex^ extremely refembling
the natural^ and the pitch-fone — Volcanos
w)hich have not this fone^ and others in
'which it is found more or lefs — Magnefa
not one of the elements of the pitch-fone of
volcanos^ as fame have thought — Intere/i-
ing ohfervaiion of the cbajige of petroflex
into pitch-fone — Chemical analyfis of thefe
two ft ones agreeing with this ohfervaiion —
Frobability that fome volcanic pitch-ftones

are

- ( 221 )

are derived from the nofi'Volcaiilc'—'Our'
common Jire equally vitrifies the Euganean
lavas, and thofe of other volcanos — Singu-
lar ohfervation relative to the eafy fufion of
feltfpars — Euganean bafaltes the produBs
of fire — One of the fiones of thefe jnoun-
tains formed in prifms in one place in the
dry 'way, and in another in the humid —
Confirmation of the affertion, that it can
only be determined by local circnmfiances,
ivhich of the ttvo modes Nature has em-
ployed in the conformation of bafaltes.

I

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

better

( 222 )

better qualified to aid my refearches ; tlie
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 obfervations relative to them*

Having made feveral excurfions with
this able guide, I examined the produces
I met with at my ieifure, and feledted thofe
that appeared mod fuitable to my purpofe 5
feveral of which I {hall now proceed to
defcribe ; as they are extremely well ad-
apted to form a comparifon between the
Paduan rocks and thofe of other countries
equally volcanic, which I vifited ; as alfo
to fhew the nature cf the modifications
caufed in both by fire ; which comparative
obfervations, I flatter myfelf, will not a
little conduce to enlarge the fphere of our
knowledge refpedting volcanos *.

I repaired,

"^ * At firft viewj it may, perhaps, appear fuperfluous
that I fhould fay any thing on the Euganean produ6ts,
as a Defcripiive Catalogue has aleady been given of
them by Sir John Strange. This naturahft has un-
doubtedly

( 223 )

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 foffilhlftory of thefe
mountains, the volcanization of which he firft difco-
vered and made known. We are hkewife greatly in-
debted to him for the catalogue he has annexed, and
which forms a kind of appendix, to his hiilory. But,
belides that 1 frequently met with obje£ls diiFerent 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 chara£lerize, the Euganean products I met with in
my excurfions, in the fame manner as I have defcribed
thofe of the two Sicilies : Sir J. Strange v/as fatisfied
with giving only fim.ple indications of them ; nor do I
think I {hall in the lead detract from the merit of this
excellent author, if I fay thefe indications were not al-
ways the moil accurate ; fuch a defedl; being lefs im-
putable to him than to the time in which he wrote 5
fince It is only within thefe few years that the minera-
logy of volcanos has been iludied with precifion and
accuracy.

X (hall take this opportunity to anfv/er a quef-
tion which may be alked ; which Is : Why, if I in-
tended to give a lithological eflay on the l^aduan volca-
noes, I did not mention it in the Introdufliicn, where I
enumerate the principal heads of the work. I reply

that,

( ^H )

ated nearly at the foot of the Euganesiti
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 firft has an argillaceous bafe, a
toarfe grain, and blackifh colour. It fhines
in many parts with black micaceous points,
and is fprinkled with reddifh fpots, like
thofe of feltfpar, in many oriental porphy-
ries ; and which are no other than fcaly
flakes of feltfpar, accompanied with a few
black fhoerls.

that, when I wrote that Introduflion, I did not perceive
the importance of the fubje£l y and of fepafating the
obfervations 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 I
feared that I might not find fufhcient leifure to reduce
them to order, as I afterwards was enabledo

The

( .^25 )

The fecond lava, which Is of a light
grey colour, might at firft be taken for a
carbonate of lime ; but, when attentively
examined in the recent fractures, 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, with an argillaceous
fmell ; and, befides numerous particles of
black mica, it contains thick redangular felt-
fpar lamellcE.

The fhoerls, micas, and feltfpars of
thefe three lavas, when fufed in the fur-
nace, are, 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. Ill, Q^ name;

( 226 )

name j not only becaufe they are Integral
parts of this volcanic mountain, but becaufe
they 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
affeded by the lire, or thrown out un-
touched by fome volcano. All of them
contain cryftallizations of micas, fhoerls,
and feltfpars ; and thefe cryftallizations
fufe in the furnace together with the petro-
filiceous bafe.

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

C ^27 )

kinds — lavas with a petrofiliceous bafe, and
Javas with a horn-ftone bafe. The former
hive a fmooth, and, fometimes, conchoidal
frad:ure, a fine and compact texture, and
contain a confiderable quantity of flioerls
and rhomboidal feltfpars. The glafs pro-
duced from them in the furnace is white,
"with a complete fufion of the above-men-
tioned cryftaUizationSi.

The lavas with a horn-ftone 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 hiicas. One of thefe lavas
bears the moft 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. Thefe 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 almoft always placed
in the fame diredion. This obfervation is of
confiderable importance ; firft, becaufe it
Q^ 2 {hows

( 228 ]

fhows that this rock was once fluid from
the action of the fire ; fince otherwife thefe
innumerable vacuities woiild 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 cryftallized carbonate of lime.

This lava is likewife remarkable for the
large fize of the Ihoerls it contains ; feveral
of which 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 cryftals of -fpecular iron.
Both when detached, and when incorpo-
rated with the lava, they melt, in the fur-
nace, into a black, compad: enamel, giving
fparks copioufly with fteel, and of a luftre
little inferior to that of the fhoerls them-
felves. Fufion fucceeds equally in the other

lavas

( 229 )

lavas of the horn-ftone bafe, with the vitri-
fication of the fhoerls, feltfpars, and micas.

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

* Opufc. Seek, di Mllano, t. i. In 410. This de-
fcription was read to the Royal Society in 1774, and
is Inferted in the Philof. Tranfa^. vol. Ixv. part i» far
1775. T.

0^3 ^P^'^rs,

( 230 )

fpars, mica, and {hoerls, are very conrpicu-'
ous to the eye. The ilioerls are rhomboidal
prifms, a line, or two lines, in length, at
the mofl, and about half as broad, femi-
tranfparent, of a whitifh colour, fliining
but little on the farface, but very confidera-
bly in the frad:ures, and with a luftre of
changeable colours. The mica is, for the
moft 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 flioerls, which
are, for the moil part, linear, are but few.
They are all three contained in a petrofiii-
ceous pafte, become earthy by decompo-
fition, and, at the furface of the prifmatic
columns, almoll pulverulent, and of the co-
lour of a dead leaf; but internally it pre-
ferves the charatfler of the petrofilex, giving
fparks more or lefs with fteel, 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 £a^
fion take<^ place in the fhoerls, but not com-
pletely in the feltfpars.

From this defcrlption we perceive that
this mafs of columns cannot properly be
called granitous ; the generality of natu-
ralifts, and the mod 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 conneding ground or cement. But
here the fhoerls, the mica, and the feltfpars
are enveloped in a pefrofiliceous pafte ;
whence we ought rather to denominate
thefe columns porphyritic. The fame is
true of the remaining mafs of Monte Roflb,
which is almoft entirely formed of the fame
rock.

Under this bafaltlform group we find

numerous globes of the fame rock, which I

judge to be pieces of prifms that have fallen

down and become round by the eroiion of

0^4 their

( 232 )

tlieir angles, in confequence of the decom-
pofition they have fuffered by time and
the humid elements ; as it cannot be fup-
pofed that their globular figure has been
produced by their being rolled by the wa-
ters, fnice there is here no trace of either
river or torrent, and their decompofition is,
beiides, 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. The fides of this cavity exhibit very
apparent prifm.s ; though not fo perfedly
charadterized as thofe before defcribed.
Should other parts of the mountain be dug
into, it is probable that other groups would
be difcovered.

This certainly is not the only place pro-
ductive of thefe figured ftones ; for we find
prodigious maifes of them at Monte Or-

tone.

( '^SS )

tone, rudely formed, it is true, but very
diftingulfliable. They confift of a lava of
a cinereous grey colour, of a petrofiliceous
bafe, and marked, in many parts, with thin
reddiih flreaks parallel to each other. A
confiderable number of rhomboidal, fhin-
ing, and tranfparent feltfpars, 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-
amel, with the fufion of the feltfpars and
the micas. In feveral parts of the moun-
tain, when we dig into it, we find imper-
fed prifms ; and they frequently projed:
out near the fummit, and on the fides ; as
we may obferve in the road leading to
Praglia. The mountain is 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-
compofition is obfervable at Monte RoiTo,
the earth of which is, in a great meafure,
a mixture of fragments of micas, feltfpars,
and fhoerls.

The

( 234 )

-The Euganean mountains, which form'
inSiTes, for iht moil part conical, fome de-
tached, and others coiitigiious at their bafes,
are principallv compofed of lavas, with
which, in feveral of them, are mixed cal-
careous carbonates. Thefe two kinds of
ftones are of fome value to the Venetians,
w^ho life the lavas, which they call mafegnsy
to pave the ftreets, and the carbonates to
make lime. There are therefore here fe-
veral quarries, fome of which are now
worked, while other^^, that are either ex-
haufted^ or become lefs productive, 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 extremely
convenient for obferving in their fides the
flcny fubftances 1 wiihed 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

( ^35 )

\^rh!ch 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 ftone in pieces with pickaxes, availing
himfeif of certain vertical fiffures, which
greatly facilitate the labour. Mines are
likewife 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 diilant, the lava of
the mountain is truly granitous, and the
granite has for its bafe the feltfpar, which
is fo abundant that it compofes the greater
part of the rock. It would be fuperfiuous
to defcribe it, as it is perfectly fimilar, even
in its cryftalilzation, to that of Monte Roflb
and Monte Ortone. Befides the feltfpars,
which, by their brilliancy and other exclu-
five characters, immediately declare their
jiature, certain white fpots prefent them-

felves

' (236)

felves to the eye, which at firft view may
excite a doubt to what kind of ft nes they
appertain ; but, when examined attentively
and under different refledions of the light,
we are convinced that they are t:ue felt-
fpars, but in part calcmed. Thefe fellipars
are accompanied with the ufual hexagonal
micas, and fome fhoerlaceous points.

This granite, liquefied by the volcanic
firej reminds me of the great adivity re-
quifite in our common fires, for the fufion
of granites that are not volcanic, and even
of thofe which are ; as I have fhown in'
Chap. XII. I have fince thought that pof-
fibiy fo great a degree of heat was not ne-
ceiTary in the prefent inftanee, from this
granitous lava being deprived of quartz,
one of the elements of the granites on
which I made my experiments, and which
certainly is that among them mc ii refrado-
jy to fufion. 1 have found, in fa£t, that
this lava, Vv^hen continued a long time in
the furnace, affords a vitreous produd; of a
black colour, and neaiiy homogeneous,

fome

C ^2>1 )
Ibme feltfpars only being perceivable in it
in the form of white fpots.

I have faid, a little above, that black mi-
ca is one of the component parts of this
granite. 1 fhall 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
Ihares with other black micas, before de-
fcribed, and with almoft all I fhall 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.
fomeof them I was fhown this quality by
Sig. xA^rduino. 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 we
may perceive that they confifl of delicately

thin

( 238 )

thin and femitranrparent lamina, whkllj
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 blackifh eolour^
and femitranfparent.

The magnetic property of thefe micas,
among the many I have examined, I have
found in none which enter into the compo-
fitlon of granites not affected by the fire.
In my return by land from Conftantinople
to Italy, I colleded fpecimens of the flones
compofmg the mountains over which my
road led me, and, among others, of a con-
fiderable 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 made experiments with the magnet .|
but I did not find one, whatever v^'as its
colour, Vv'hich fhowed the leaft fign of at^
tradlion. In feveral of them, indeed, I

found

( 239 )

found it after they had been expofed for
fome 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 confirmaticn of
their volcanlzation.

Before I difmifs the quarries of Monte
Merlo, I fhall briefly ftate two fads not
undeferving the attention of the reader;
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
amethyfl:ine ; it is tranfparent, fomewhat
unduous 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, v^'ithin 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 muft have altered the quartz, by

depriving

C 240 )

depriving It of its tranfparency, and render-*
ing it full of cracks, and extremely friable ;
all which changes follow on expofing it a
fhort 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 their
amethyfline 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,
v;hen fiery torrents meet with extraneous
ftones in their paflage. I am, in fad, of
opinion, that thefe fmall maffes of quartz have
been produced pofterior to the congelation of
the lava, by the filtration of water im.preg-
nated with the molecules of quartz, which
lias penetrated into fome fmall 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

( HI )

The other fad is very fimilar to this, and
liiay be explained in the fame manner. It
relates to the large pieces of fhoerl which
are contained in this volcanic rock, and are
difcovered on its being broken into pieces, in
the fame 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 iri
the largenefs of their fize, they perfedly
refemble thofe of the porous lava, with the
horn-Hone bafe, of Monte Donati, 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-
tallized flioerls, is the excluUve property of
thofe that are volcanic. Though, in the
courfe of this work, I believe, I have only
mentioned the ihoerls of Mont^ koflb, at

VOL. Ill, R Etna,

( 242 }

Etna, as poffefling the property of ftrongly
moving the magnetic needle*, I did not
fail to make the fame examination relative
to numerous ilioerls of the Phlegrean Fields
and Eolian Ifles, 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 Ihoerls,
whatever was their colour, fome of which
were detached from granites, and others
found folitary. This obfervation, Vi'hen
treating of the Euganean mountains, ap-
pears 10 me too important to be omit-
ted.

Thefe fhoerlaceous lumps or groups, I am
of opinion, muft have been produced in the
granitous rock by filtration, with this fingle
dilFerence, 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 Chap. VII.

Having

( 243 )

Having examined fome of the quarrieS
which furniih volcanic ftones, I proceeded
to vidt thofe where carbonate of lime is
dug, of which ftone there is no fcarcity in
the Euganean mountains. Such are the
quarries of Battaglia, Fraffinelle, and Saint
James, fituated on the declivities of theS
Monte Grande, above Teoio. Before we
reach the lava of Battaglia, we meet with
this carbonate. It is fciffile, and eafily di-
vides in flakes, for the moft 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 5
from thofe of one inch or lefs to thofe of a
foot. We feldom meet with flony 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 carbooates, con-
R 2, tain

( 244 )

tain likewife nints. On examining tliofe
of the quarry of Battaglla, 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
neceflary to defcribe both the carbonate of
lime and the fliut.

The lime-ilone is white, compact, not
very heavy, compofed of impalpable parti-
cles, foft to the touch, with a fmooth and
Ibmetimes conchoidal fradure, and break-
ing into obtufe and amorphous fragments.
It is diflblved by acids with confiderable
effervefcence. Both internally, and on the
furface of this white ftone, 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
fmooth, and aimoft 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 ftrongly with fteel.
Notwithftanding their great hardnefs, how-
ever, the generality of thefe flints eafily
break into fmall pieces under the hammer.
Some of them, in the quarry of Battaglia,
are placed between the ftrata 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 Itme into filex ; and the
opinion that this is really the fad has been
adopted by many,

A piece which exhibits this appearance
has one part of it w^hite j which colour in-
fenfibly difappears, and is fucceeded by a
reddifli tinge, that gradually increafes till
the remainder of the piece at length affumes
the red, browri, or black colour which is
R 3 proper

( 246 )

proper to this flint. The change of colour is
accompanied by a difference in the hard-
nefs, which fucceflively increafes, as appears
from its fclntillation with fteel ; the v/hite
part of the ftone yielding no fparks ; the
light red, very few ; but the deep red, or
black, affording 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 eifervefcence arifes,
which becomes lefs fenfible in the pale red
parts, diminiihing as that colour increafes,
until no appearance of it is difcoverable
wher^ the rednefs is deepeft, and the fcintiU
lation with fteel ilrongefl. Thefe charac-
ters, however, to the chemical eye are not
decifive of the fad: in queftion. For, not
to mention that difference of colour never
couflitutes 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 prefence of carbo-
nate of lirne 5 fmce, though it has been con-
fidered as the diflinguifhing property of
calcareous carbonates, that they do not af-
ford

( H7 )

ford fparks with fleel, it has been proved
that there are feveral which have this qua-
lity. I poffefs feveral fpecimens of mar-
bles, that I colleded fome years fince in
the quarries of Garrara, which when, ftruck
agair^fl fl^el 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, others
of a very light red, others flill redder, and
others of a deep red. The refults were as
follow ;

In the fragments of the firft kind, I

found the quantity of lime very great, and

that of filex very fmall ; negleding, at that

time, the . carbonic acid gas, and the fmall

R 4 portion

( h8 )

portion of alumine. 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
fjnall.

■prom thefe fa6ls it appeared to me evi-
dent, that it was not neceflary to have re-
courfe to an imaginary tranfmutation, fmce
the gradations in the fame ftone above de-
fcribed might be explained without it.
Thofe fluits which make a part of the fame
ftratum with the calcareous carbonates, flaew
that they were formed at the fame time with
them ; that is, when they were produced by
the numerous fediments of the fea-wat:er
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

with

( 249 )

with the latter, generating mixtures of the
two earths fuch as they have been found
when analyfed.

It muft, however, be obferved, 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 cruft which is obfervable in
a multitude of other flints. It is very pof-
fible that the produdlon of thefe globes and
leni'es may be pofterior, and caufed by fil-
tration, after the formation of the calcareous
ftrata.

I fhall fay nothing of other quarries of
Ume-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 fl:ones which derive
their origin from fire, I fhall now proceed
|o fpeak of a kind of lava, the mod: noble

and

( 250 _>

and beautiful which any volcanos afford.
Near Teolo rifes a fmall hill, called the
Monte del Boldu, principally compofed of
llony globes of various fizes, difpofed in
flrata, tenacioully adherent, with a central
nucleus. Thefe globes are of an iron cb-
lour, and fprinkled over in every part with
lucid points, which at firft view I imagined
micaceous ; but, on examining them atten-
tively, t 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 with 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*
pad;.

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

( ^5^ )

wards difcovered, in a fmall valley, to the
fouth, below Bajamonte. It there forms a
vein about thirty-five feet long, and nine
and a half broad. On the fiirface it is fo
much decompofed, that it will crumble be-*
tween the fingers. At a little depth it is
lefs foft, but always retains a confiderable
degree of friability.. The pieces into whichi
this vein breaks frequently take an oval
foriEn, which they likewife have when
broken into fmaller pieces. To render
more apparent the colour of this ftone, it is
proper to wet it ; for wetting is to rough
ftones a kind of half polifh. It then has
the exa<5t: appearance of the pitch-ftones.
In. fome parts it is of a. red colour ; fome-
times pale, fometimes more lively, and
fpmetifnes. inclining to a yellow ; in which
latter cafe, it refembles certain- kind?- of amr
ber; but in other parts the. colour is a^
mixture of '.bluej .green, and white, but all
of them very pale. The fractures are al-
ways amorphous, of unequal furface, and
little- brilliancy'i The thinner flakes are
tranfparent ; as is the property of fome

pitch-

{ 252 )

plich-ftones. This lava contains unequally
diftributed feltfpars of a flat form, friable,
and not very brilliant. Every ftroke with
the fteel breaks off fome pieces, but extrads
no fparks.

A few hours in the furnace deprive this
flone of its colours, rendering it of an afh
grey : it likewife lofes its friability and
foftnefs, and becomes capable of giving
fparks with fleel ; 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 fuficn of the feltfpars.

The fmall valley of Bajamonte is not,
liowever, the only place in which this
pitch-ftone lava is found ; it is met with
in feveral others ; as at Monte Sieva, an4
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 exactly the
£ colour

( ^53 )

colour and luftre of pitch, and contakis
numerous feltfpars. In its external appear-
ance it does not diiFer from that before
dcfcribed. It has, however, one peculiarity
which muft 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 fome parts of this
rock, either by a more violent adion of
the fire, or becaufe they were more eafily
vitrlfiable, have paiTed into the ftate of
pumice.

In the fame Monte Sieva, befides a lava

with

( 254 )

with a petrorilicedus bafe, which, from its
compad;nefs, extremely refembles the natu-^
ral petrolilex, but which is fufible in the
furnace, we find another vein of pitch-
ftone lava, but of much greater extent, and
which is difpofed almoft vertically. On
digging into this vein, we find very beau-
tiful and well preferved pieces of pitch-
ftone lava. For the mod part it has the
colour of refin, an elegant luftre, a fine
grain, and great compactnefs. It is fmooth
and clear in the fradlure, 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 afped:.

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
ads with refped to them as a gluten or
cement. Thefe pieces have not been rolled
by a ftreani or waves, and thereby become
round, but are amorphous, and with acute

angles.

( ^5S )

angles. It is evident, therefore, that this
lava has been broken by fome violent agent ;
and its pieces afcerv^ards have been taken
up, and inclofed within the ftony fubftance,
which, when carefully examined, is found
to be only a conglutination of very fine
duft of the fame pitch-ftone ; which alfo
contains Hones of feveral other kinds.

At Cataio, where is the villa of the Mar-
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 not, how-
ever, referable 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

( 25^ )

©n 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
piteh-ftone lavas, becaufe they refemble in
their external appearance the ftone defigned
hj that name. I have likewife 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-
ilones may be fufed, and the infufibility
of the true pitch-ftone even in a violent
fire *.

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

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

nace.

( 257 )

nace. They were, in the whole, nine 5
three from the ifle of Elba ; one cirierltious
and almoft opake ; the fecond femitranfpa-
rent and yellowlfh ; and the third opake
and inclining to black : three from Germa-
ny ; the firft yellow, the fecond red, the
third black, 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, fliewed no fign of liquefac-
tion ; but only became white, extremely
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 fufible 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

( 258 )

mann found the portion of filex to be
greateft, that of alumine, little, and that of
lime, leaft.

Another, analyzed by Wiegleb, gave

Silex - - " 6^

Alumine - - - i6

Iron - - - 5

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

A third by Gmelin

Silex - - " go

Alumine - - - 7

Iron - . - - 3

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

* Kirwan's Mineralogy.

Pitch-

( 259

)

Pitch-ftone lava below Bajamontej

Silex

71

Alumine

- 18

Lime

4

Iron

5

Pltch-ftone lava of Monte Sleva in beau-
tiful and well preferved pieces,

Silex

'-

ni

Alumine

•

14

Lime

.

8

Iron

-

3l

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

( 2^ )

find that the principle moft abounding in
thefe fix fl:ones is the filex ; that the alu-
mine is but in a moderate or finall propor-
tion ; as are hkewife the lime and iron
when they enter into the compofition of
thefe fliones. It is therefore evident that
thefe fix fi:ones are of the fame fpecies ;
nor can the infufibility of feveral pitch-
ftones, which are not volcanic, diftinguifh
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
Muflato, of which 1 (hall prefently treat,
require a continuance of feveral days in the
furnace before they are completely fufed.
Some pitch-flone lavas of the iHands of
Ponza, which are of a pale white colour,
and of a fmcoth and fhining fra6lure, 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, Jl is remarkable that almoft all vol-
canic

( 2(31 )

c&nic pkch-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 Euganean mountains
befides rhofe already mentioned, have in-
duced Father Terzi, a Benedictine, to fup-

- pofe that they were no other than real
glafs, an opinion which he publilhed a few
years fince in fome letters on the Euganean
products. He informs us that he difcovered
large veins of them in the Monte del MuiTato,
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 this branch of
natural fcience, repaired to the mountains,
and foon difcovered the error Vv^hich had
been committed by the good Father mif-
S 3 taking

{ 262 ) .

taking tliefe pitch-ftone lavas for glafs,
which error he detecfled and proved in a
Memoir entitled On certain parts of the
Paduan Mountains ^.

In September 1792, the Marchefe Anto-
nio Orologio and myfelf, having made an
excuriion to the Euganean mountains, to
vifit this celebrated naturalifb, who refided
at the village of Galzignano, he con^-
duded us to Monte del MufTato, where
thefe fuppofed veins of glafs were to be
feen ; but we found that they were only
large mafTes of pltch-flone 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 two 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 dg' Monti Padovaiii.

many

( ^^i )

;many places, includes extraneous bodies,
fome of which are of confiderable import-
ance to volcanic enquiries. Thefe are
fmall pieces of horn-ftone poflefiing that
porofity which charadlerizes them for true
lavas. One of the fpecimens above men-
tioned contains a fragment of this kind
two inches in thicknefs, extrem.elv perfed:,
and very porous. The vacuities are round
and elliptical : fatisfadlory 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, which is that of tur-
pentine, only much darker and lefs lively.:
and in its confiftence ; except that it forms
unmixed mafles, and contains amorphous
feltfpars, of little or no brilliancy. Among
all the pitch-ftone lavas of the Euganean
•mountains that fell under my obfervation,
.this is the moft compad:, heavy, and hard.
The eye alone, however, is fufficient .to
difcern the great difference between thefe
S4 pitch-

( 264 )

pltcli-ftone lavas and volcanic glafs. The
idea of volcanic glafs is derived from that
we have from our common glafles ; the
infeparable chara6:ers of which, as we well
know, are, that they fhould have a ihining
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 fmooth and clear, or, as we fre-
quently find, with waving and curved
ftreaks ; not to mention its tranfparency, a
quality known to every one, and, in glafs,one
of the mod valuable. The fame, precifely,
are the characters of the greater part of
volcanic glaffes ; but the defcription of the
pitch-flone lavas is very different. They
have commonly a dead and dull luftre ;
their pafte is fine, indeed, but not compa-
rable in finenefs to that of glafs ; they are
lefs fmooth in the fradures, lefs (harp and
cutting at the edges, and have little or no
tranfparency. They are llkewife diftin-
guifhed by another property from volcanic
glafles, the greater part of which are fuffi-

ciently

( ^65 )

clently hard to extra*^ fparks from fteel,
that is to fay, to melt it : on the contrary, I
was never able to extract the fmalleft fpark
from the pitch-ftone lavas above mentioned,
though I made the experiment on them
with the beft fteel. They are therefore lefs
hard than volcanic glafs, as is indeed appa-
rent from the facility with which pieces fly
off at every ftroke. To thefe evident dilli-
milarities we may likewife add the weight,
which in pieces of the fame fize is always
greater in volcanic glafs than in pitch-ltone
lavas.

Father Terzl may, however, eafily con-
vince himfelf that thofe 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 produdt a true
enamel, exhibiting a vitreous afped: not at
all difcoverable in the pitch-ftone lava from
which it was produced. This is true, like-
wife, of the veins of Monte MuiTato ; and
ihews that the pitch-ilone lavas muil not

only

20(

ois]3r be excluded from the clafs of .vokaniG
glaiks, but even from that of enamels.

When, in the year 1789, I made an ex-
curlion over the mountains of Padua, ira
fearch of volcanic objedl:^, accompanied by
the Marchefe Orologio, we, at Praglia, w^ere
received and moll 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 produdtSj
colleded 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.

T,he firft, which, according to the ac-
count he gave us, was brought from Schi-
vanoja, is a mixture of amorphous, white,
and friable feitfpar, and black, prifmatic, and
extremely brilliant (hoerls, much refenibling
fome fpecies of tourmalins. From this mix-
ture is obtained, in the furnace, an extreme-

{ 26; )

!y. black enamel, of the greateil compad-
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 produdt, which is from Mon-
te Merlo, confifts of an aggregate of ex-
tremely white and fhining half-cryftallized
feltfpars, of a changeable colour, which ia
the furnace produce a white, and fpungy,
but hard glafs.

The third, which is from the fame moun-
tain, at firfh 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 fparks with fteel ; inflated and rendered
fpungy by the adion of fire, and aeriform
fubftances. The furnace perfectly vitrifies
it.

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

were

( ?68 )

were true pitch- flone lavas, though Father
Terzi believed them to be real glafles.

I had not time to certify myfelf with re-
fpe<3: to the places where thefe productions
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 refped: to the two produdts of whiph
I ihall now proceed to fpeak, as I found
them precifely in the places which ha.d
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-
^ompofitioUj and, confequently, has loft, in
a great degree, its external charad:ers, the
interior mafs may at firft deceive the eye of
the obferver, and induce him to confider it

as

( 269 )

as real glafs. The afped: is fmooth and
ihining, like that of glafs ; but with fome
undiuofity, as is the property of fome lefs
perfed: volcanic glafTes. But on examining,
with greater attention, the pieces recently
fradured, we do not find in them the cha-
raderiftics of volcanic glafs ; as they have
not the finenefs of confiftence, 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, which cannot be done with impu-
nity by volcanic glafles.

We know, likewife, that the primordial
rocks, when they are changed by the adion
of fubterranean fires into the nature of glais,
are no longer recognizable ; as they have
loft their primitive ftrudure, and are redu-
ced, together with the extraneous fabflances
they contain, as flioerls and feltfpars, to one
fimilar and homogeneous rnafs; whereas,
en the contrary, the vein in quefiion fuffi-
ciently declares its origin, which is a petro-
filex of a dark green colour, a fradure

fome what

( 270 )

fomewhat fcaly and conchoidal, of a grairi
moderately fine, 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 confiderable), do not form one ho-
mogeneous pafte with the bafe, but are both
in a ftate of the greatefl prefervation. The
feltfpars exhibit a cryftallized form, but it is
impoffible to define it v/here the petrofilex
has not been altered. It is not the fame
with the'fuperficial cruft, the bafe of which,
having been in part deftroyed, holds thefe
ftones but feebly ; fo that they may eafily
be detached entire with a knife ; when they
appear to be prifraatic cryftals, with tetra-
hedral redangular 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, arid con-
taining the fame micas and feltfpars ; but it
is of a pale green colour, and tolerably
I hard :

( 271 )

hard : it has not, however, the brilliancy c^
the former. Both thefe roeks produce in
the furnace a greyifh enamel, with an entire
fufion of the feltfpars, but not of the micas,
which leave black points within the enameL

The other producft of which I went in
fearch, according to the diredlions given
me by Father Terzi, was, in hke mmner,
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-
racters 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 v/irhout delay to
Valfanzibio ; where I found more than one
piece of it, not infixed in the earth, nor in
the midft of any rock or ftony vein, but
loofe, and fcattered over the ground, like

ilones

Hones 111 a public road. I was fomeWnat
furprifed at this ; and, on making enquiries
of fome peafants on the fpot, 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 Valfanzibio, and,
finding it ufelefs, had thrown it away therCi
I repaired, accordingly, to the place they
pointed out, and found that it was, without
the lead doubt, of the fame kind. I, after-
wards, learned from the keepers of the gar-
den, that it had been procured from the fco-
rix of the furnaces of Murano, near Venice.

I fhall conclude this account of the vol-
canic fpecimens of the Euganean mountains
iliown me by Father Terzi, in his cabinet
of natural curiofities, with mentioning one
more, which in his opinion was a volcanic
glafs, and had been found detached on Mon-
te Merlo. To this, likewife, 1 cannot refufe
the appellation of glafs. It is, like the for-
mer, black, compadl, and heavy. As I did
not go to the place where it was found, I

cannot

( ^IZ )

cannot pronounce with certainty relative to
its origin. It is poffible that this glals may
be the produdion of thofe very ancient vol-
canos, fince Sir John Strange, at number 62
of his Catalogue before cited, mentions
fome pieces of foffil glafs, but which are fo-
iitary and accidental, found in fome parts of
the Euganean mountains. It is not, how-
ever, abfolutely impoffible but that it may
be glafs from the furnace ; at leaft the
accident of the glafs of Murano ought to
teach us to be cautious, and fufpend our
judgment 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 from fire, while
we are uncertain whether that fire was, or
was not, volcanic. For, even though the
pieces found fhould be really volcanic, they
cannot afford a certain proof of the volcani-
zation of the place where they are found
detached. Of this I can produce an inftance
which happened to myfelf in a curfory vifit
that i made to Capo Colonne, a promontory
VOL, in. T of

( 274 )

of Attica diftant twenty miles from Athetls^,
when, in 1785, I accompanied his Excel-
lency the Venetian Envoy, the Cavaiiere
Zulian, to Conilantinople. I there found
pumices fcattered over the ground, to my
no little furprife, as the place exhibited no
indications of being volcanic. They were
of that kind which, from their levity, fwim
in water ; and, being of a globofe figure, I
fufpeded that they had once fiov/ed. 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 dafhing of the waves, I
found three other fimilar pumices, which
-authorifed me to conclude that thofe on
the height above, 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
thaX many iilands in the Archipelago are

volcanic ;

( '^IS )
volcanic ; and that Santorine, in particular^
is only one immenfe mine of pumices *,

The objedions which may be made to
the relations that afcribe a volcanic origla
to a country, merely becaufe certain fub*
fiances that bear the marks of fubterraneaa
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 muft 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 iffiied from the entrails of a mountain,
or volcanic veins and ftrata are found in its
fiffures.

There afe many V\rritei*s 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 d,^D,j

( ^7^ )
deny the poffibility of there having been a
volcano in fuch places ; but I mud ajffirni
that thefe indications are equivocal, and,
therefore, may be fallacious. It is true
that many volcanic producls are black,
with a colour varying from the blacknefs
of iron to a greyifli 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 illes. But it is likev/ife true, that
in many others the blacknefs dirainiOies 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 lofl 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 two volcanos, to per-
ceive thefe faccefiive changes. Every lava,
however, though of a recent date, is not
black. The colour which is proper to the

primordial

( 277 )

primordial rocks frequently does not difap-
pear in confequence of the adion of fire.
The colour of many lavas approaches to a
black, becaufe that was the colour of their
rerpe(ftive primitive rocks, as we fee in the
lavas with a horn-ftone bafe. In 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 glaiTes produced from
thefe rocks when fufed in the crucible. It
is therefore certain that the colour of the
produ(5ts alone is not a certain indication of
a volcaao.

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

( 2^8 )

from his own obfervatioii that thele
matters have really fuffered the adiion of
fire, if he wilhes to convince the philofo-
phical world he muft fpecify their nature j
^s whether they are puzzolanas, adie?,
glalTes, enamels, fcorise 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 extinguiihed volcano the remains of a
current of lava, unlefs he properly defcribes
it, fmce the advancement of this fcience
depends entirely on exadt defcriptions of
products affeded by the fire. The moft
able volcanifts of the prefent time write
after the manner of accurate mineralogifts.
Aipong thefe volcanifts, the firft place is
certainly due to M. Faujas de Saint Fond,
as is fufBciently proved by his Mineralogy
^ Volcanos.

And here I cannot refrain from making
foix^e obfervations relative t9 l^vaa in gene-

raL

( ^79 )

ral. By the word lava is under flood, as
every one knows, a liquefied ftony fab-
ftanee which has been in motion. Whea
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 yolcani-
zation of the mountain from other figns,
and fee thefe ftony ftrata arifmg from its
fummit^ and tending downwards, with the
wavy appearance and inequalities before
mentioned, though there fhould be no ap-
parent indication of a crater. When we
afcend to the fummit of thofe Eolian Ifles
in which the remains of craters are no
longer vilible, we immediately difcover
confpicuous currents of lava. There may,
however, be cafes, with refpedt to moun-
tains that have fuffered the adion of fire<j
in vv^hicb, from want of local circurnftances,
T 4 we

( 2^0 )

we may remain in doubt whether the vol-
canized rocks that prefent themfelves to
our view, have ever adually flowed. This
doubt I experienced myfelf, when I firil
vifited the Euganean mountains, in confe-
quence of my obfervations relative to the
primitive rocks, and the experiments I had
made on lavas in the furnace. I confidered
that it was poffible the rocks of the Euga-
nean hills might never have flowed in cur-
rents, and confequently that they could not
have been lavas, though they might bear
very fenfible marks 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
loo far from my fubjed, I will here briefly
defcribe.

In Chap. XI, I have fpoken of the fufion
of fome porphyries with a horn-ilone 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,

aiTumed

( 28l )

aflumed a fmooth and vitreous furface.
Their internal grain acquired an afpe<9:
rather vitreous than filiceou , 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
and angles ; which prefervation of the fi-
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 b'lella^ which
ilrongly refills the fire. It is commonly

found

( 282 )

found to be compofed of alomine, filex^
and a very fmall quantity of lime. It is
ufually refradory to the fire of a glafs
furnace ; but fometimes will fufe when^ it
contains a rather larger proportion of lime.
Of this kind of earth I made feme fmali
fpheres and cubes, which I left four or
iive hours in the furnace ; when the vitri-
fication had penetrated to the depth of two
thirds of a line, and in fome even a whole
line, and the central p^rt had become femi-
vkreous,,

Similar effects take place in lavas. Their
furface affumes an enamel or vitreous
afped:, which in the internal part is lefs
apparent. In forae, however, we find
points which have become vitreous, thougl^
thefe lavas before did not contain a fingle
atom of glafs. In general, they lofe that
grain and texture, w^hich indicate the
primitive rocks w^hence they were derived,
and they all, or nearly all, may be called
vitreous^

( 283 )

Thus we have a prodigious number of
foffil produdions which have the moft fpe-^
cious appearances of lavas, and vitreous
lavas, though they have never fuffered li-
quefadion ; as is incontrovertibly proved
by the pieces, which, when they come out
of the furnace, retain exad:ly the configu-
ration ihtj had before they were expofed
to the lire.

Inflrudted by thefe fads, I confefs that
the firfl 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 rocks, vvhich in a great part
form thefe mountains, owed their origin to
T^olcanic eruptions, or were pre-exiftent 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 w^here we at prefent
fee them. Every doubt however was re-
moved, and I remained convinced that

thefe

( 284 )

ihefe prodigious maiTes of rocks were
igneous eruptions, or, in fad:, currents of
lava, of which the porofity of fome of
them was a very evident and fatisfadory
proof. It is indubitable that the elaftid
gafes, which generate pores and vacuities
in the recks a^ted on by fire, cannot pro-
duce that tfFecl unlefs thefe rocks .are foft-
ened fufEciently to yield to the expanfive
force of thefe aeriform fubflances, which
muft precifely happen in their adlual lique-
fadion. This, though fufEciently evident
in irfelfj is undeniably proved by experi-
ments I made in the furnace. When the
porphyries with a petrofiliceous or horn-
HouQ bafe, and, generally, when compact
lavas aiTumed the fimple vitreous varniflb,
and fomev^bat of a vitreous afped: inter-
nally, but Vv'ithout the pieces conglutinating
and forming one fingle uniform mafs, they
rarely or never contained bubbles ; which ,
on the contrary, were confpicuous and nu-
merous when the fufion was complete, and
the larger, the greater the degree of liqui-.
dity produced by the fire in the ftony bodies.

Th©

( 285 )

The porofity of volcanic rocks Is, therefofej
a deciiive 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 fhail 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 negle(3:ed to note it in my
journal, an omiilion of little importance to
the truth of the fadt ; which declivity is
compofed of a rock v^^ith a horn-ftone bafe,
containing fekfpathofe cryftals, and full,
both on the furface and in the internal
parts, of round vacuities, fuch, precifely,
as are ufualiy produced in lavas by aeriform
fluids*

I fliali make a few more obfervations on
the Euganean lavas ; and ihall notice that
one of them containing bubbles, and that
in a confiderable number, is found in im-
menfe quantities in, and on the fide of, the
road leading from Bajamonte to Rua*
1 This

( 286 )

This lava, which has for its bafe the horii^
ftohe, and emits a ftrong argillaceous odour,
has the colour of a dead leaf, a grain fdme-
what fandy, 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 cryilalllzed
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-vsreft of a declivity of Rua
we find great mafles of a volcanic rock that
has fallen do-wii, 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 vv'hich are
of different colours (fome being afh-grey,
others red, others of a pale violet), is of a
petrofiliceous bafe, with an eartby gfain,
and contains, befides hexagonal micas with
oblique fides^ tranfparent feltfpars, cubical,

prifmaticalj

( 287 )

prifmaticaljand fometimes amorphous^ which
give fparks ftrongly with fteel, and form very
brilliant plates. The largeft are five lines
and three quarters In length. Each of thefe
fehfpars includes within it a fmall portion of
the petrofiliceous bafe, v/hich forms in it a
kind of nucleus, and occupies a confiderable
part of its fubftance. But to what caufe are
we to afcribethis fingularity ? I can conceive
no other method of explaining it, but by
fuppofing, that Vv'hen tlie integrant particles
of the fehfparsj diiTeminated in the earthy
and liquid bafe, united by the force of aggre-
gation in cryllialiized maffes, each of thefe
maffes included a fmall part of this bafe,
greater or lefs in quantity. The rarity of the
phenomenon, however, fuppofes a l6cal cir-
cum (lance, which had a dire'51: 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-tranfparentglafs, with black fpots,occa-

fioned

C 288 )

fioned by the micas of that colour which
have remained, in a great meafure, refra^lory*

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

This lava Is white, apd has the compad-
nefs of fine carbonates of lime, which it re-
fembles in appearance, fracfture, and weight.
It affords a few fparks with fteel, and is
diftinguifhed from other lavas by numerous
points of a delicate green, fcattered over the
white groimd ; but which, to be viewed
difl:in£tly, require a lens with a ilrong light.
When thus magnified, we find that they are
a femi-pulverous earth, which may be de-
tached with the point of a needle, and is
placed betVi^een the fiifures of minute amor-
phous maffes of fliining, v/hite, and ex-
tremely

( 239 )

tremely tranfparent quartz. ■ I know hot
whether this powder be a decoinpgirifioh of
quartz, which, however,- does not appear
very probable, as it is found deep iii-th^ih*
ternal part of the lava, where it is not in
the leaft altered ; or whether it be an ex-
traneous and adventitious fubftance;' - Be-
iides the quartzofe grains, the petrofili-ceous
bafe contains a few very fmall feltfpkrs,
which, from their changeable brilliancy^
their rhomboidal form, and ' their being
compofed of minute lamins, cannot bfe
confounded with the quartzofe grains.

It is necedary to obferve that the bads
of this lava, in the furnace, ferves' for a
flux to thefe quartzofe grains ; the refult
being a homogeneous and white enamel,
v/ithout the fmalleft 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, oppoiite

■ VOL. I IT. U Catajo,

( 290 )

Catajo, is in no refpedl different from this,
except that the quartzofe grains are not
accompanied with green fppts. It yields
in the furnace the fame volcanic produd:.

At Monte Nuovo we find feveral maffes
of a lava which deferves,oiir notice, from
its. being reduced to fuch a ftate that it is
pulverable by the mere preffure of the fin-
ger. It has an argillaceous bafe, and con-
tains an abundance of feltfpars which have
preferved their prifmatic figiu'e, but are ne-
verthelefs pulverable. It is rare, in volca-
nic places, to find feltfpars fo much injured,
even where they have been a6ted 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

{hoerls

( 291 )

{Iioerls or felffpars ; .and, in their external
characters, feem not to differ effentially
from the lava itfelf.

Among the number of the pitch-Hone
lavas already mentioned there is one which
muft peculiarly attract the attention of vol-
canifts, from the pumices it contains. Mon-
felice, one of the Euganean mountains^
which Hands detached, and is of a moderate
extent and height, is partly compofed of a
white argillaceous lava, of an earthy afped:,
in which we find this pecuHarity ; only
that, while the pumices of the.pitch-ftone
lava are derived from the parts of it being
dilated and tumefied by gafeous elaftic fub-
ftances, thofe of the prefent lava appear to
be adventitious, confifting in white globules
eafily feparable from the bafe, from whici;
probably they were taken when it was in
a fluid ftate. Except that they are lefs,
they confiderably refemble the pumiceous
globu;es of Pompeii near Vefuvius ; and
both, in the furnace, produce a fimilar
enamel.

U 2 Thh

( 292

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

Monte d'Arqua was the laft v/hich I
"vifited. Its fummit is compofed of a, grey
compact hva, which has a horn-ftone hafe,
affords fparks with fteel, and contains-mi-
caqeous and fekfpathofe cryftals, This lava
h found in fome places lir^ flrka nearly ho-
rizontal.

: To thefe lavasj which I foiind on the
fpot, while accompanied in my refearches
hy the Marchefe Orologio, I fhail add a
few others from the Monte del Catajo,
which were afterwards noticed and exa-
mined by that il'iuftrious nobleman and
naturalift, who vifited every part of that
mountain to which his villa is contiguous,
and coUedled fpecimens of the fpecies of
moft importance, obferving the places
where they were found. i\t my requeft
he tranfmitted them to me, with their fe^

vera!

( i93 )

t^erai defcrlptions, which I £hall here briefly
give the reader, only making fuch alteri'«;
tions as appear to be neceflary.

I. Is one of the fineft lavas of the Eii«
ganean mountains. Its bafe is feltfpar in
the mafs, but it is with difficulty recog-
nized from its exterior charaders, the fire
having changed it into a vitreous lava. It
is of a cinereous colour, compad, but not
very hard, on account of its numerous fif-
fures. It contains cryftallized 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 traQ: 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 Ihould 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, v/e find fev era! globes of ^ petrofilex as
flrongly characterized 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 with
a white argillaceous cruft, which attaches
to the tongue ; and contains a number of
micaceous- points, and feltfpathofe laminae.

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 afcent 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 buried with-
in the lava No. II ; and, in part, ifTues
from it, forming tortuous veins of various
fizes, and running in various directions,
one of which interfedts the decompofed
vitreous lava No. III. The bafe of this
lava is an extremely compact petrofilex ;
it is of a fine grain, accompanied with
micaceous and feltfpathofe cryflals. 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-

U 4 compofed

( ^9^ )

.dotnp^^i. iJ^ the . faiDe manner as fbma
tra6l$ . of .that .of No. I. Its bafe is argilla-
C€-ous;and it attaches to the tongue ;; the fmall
jcryftal^ s^ .black mica and fekfpar which it
contaias^ are, however, uninjured. This lava^
Jik^\f lie, iilues in veins from the body of
■that;', .-of No. IL

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

Y, Eefides feverai beds of pitch-ftone
lava, which concu-r to tbe formation of
Catajo, there is one, near the fummit,
towards the fouth-wefl, interfperfed with
inmimerable very fine white ilreaks parallel
to each other, and which form a ftrong
contrail to the red ilreaks of the pitch-ilone
lava. Thefe white ilreaks, as far as I could
difcover, are the fame lava decompofed,

.^ and

( 297 )

and perhaps rendered fuch by the filtration
of the rains which have infmuated through
the fmall fiffures of the lava.

I1.1 the furnace it changes into an enamel
lirailar to that afforded by the other pitch-
ftone 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 firf!: fummit" (the
Monte del Catajo is bifurcated) " there is a
" fpacious irregular plain with many in-
" equalities, which I incline to fufped: was
*' an ancient crater deftroyed by time, and
" filled by the falling in of its fides. We
" here find enormous mafies of a fpecies of
" breccia, or pudding-ftone, compofed 'of
" fmall fragments of many varieties of lava,
" united and bound together in a hardened
« clay."

This breccia I carefully examined, and

confider

( ^98 )

confider it as well deferving attention. Black
fhoerl in the mafs conftitutes the greatefl
part of it. It is found in pieces furrounded
by a grey earthy cruft, which attaches to
the tongue, and is a decompolition 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 fhoerlaceous point in the mid-
dle. Thefe fmall pieces are ufually angu-
lar ; whence 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 yellow colour, and a vitreous
afpe6t, which is likewlfe 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 adion of the at-
mofphere and of time. The fhoerlaceous
fragments evidently fhew that they exifted
previoufly to the vitreous fubftance ; which
paffing over them when it was in a fluid
ftate, included them v^ithin it, and formed

one

( 299 )
one body with them. They may, alfo, pof-
fibly be fmall fragments of a very ancient
lava, with a bafe of fhoerl in the mafs ; un-
lefs we rather choofe to fuppofe that fome
vein of fhoerl, broken by the impetuofity of
the elaftic gafes, and reduced to minute
pieces by the Ihock, has been thrown out
from a volcanic mouth, without having been
fufed or changed by the fire.

VII and laft Lava. Though this be fpe-
cifically the fame with No. II, it claims to
be diftind:ly 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 prifmatic 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 )

h a trapp, which, in refped tp Its confiil-
ence, and the feitfpars it contains, extreme-
ly refembles that of No. II.

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

REFLEa

( 3°^ )

REFLECTIONS and COROLLARIES.

THE fadls explained in the prefent chap--
ter are highly inftrudive, from their teach-
ing; us the nature of the different volcanic
rocks of the Euganean mountains ; but
they are ftill much more fo from their ena-
bling us to form a comparifon between thefe
volcanos and others in Italy and its vicinity,
either extioguifhed or at prefent burning.
"We are taughc by obfervation and experi-
ence, that nothing exlfts in nature detached
/ andfolitary; but that the whole is connected
with a variety of relations, and that we can
acquire an accurate knowledge of no fmgle
part but by means cf comparifon. In my
other v^^orks on phyfical fubjeds, I have
conftantly made it the primary objed: of
my itudies and refearches to analyfe and
compare the fads I difcovered with each
other, and with fimilar fads difcovered by

other

( 302 )

other authors ; and in the prefent work I
certainly fhall not depart from a method
which appears to me beft adapted to en-
large the Hmits of our knowledge of nature,
and increafe the treafure of ufeful fcience.
With this view, therefore, I fhall add the
following brief refiedions :

Though the fea is now fome miles di-
ftant froin the mountains of Padua, it is
beyond all doubt that it anciently wafhed
them ; as is proved by the calcareous car-
bonateSj and their horizontal ftratifications,
befides the marine fliells 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 iflands^
refembling thofe of Lipari, Ponza, Santo-,
rine, and innumerable others of the fame

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

kind :

( 3^3 )

kind ; except that in the very ancient vol-
canos of Padua any perceptible ignitioa
has gradually diminiihed and difappeared,
nothing remaining but fome feeble refidue
in the welhknown warm baths. This an-
tiquity, it cannot be doubted, hkewife, is
the reafon why thefe mountains, notwith-
Handing they ftill 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 eifeds 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 diminifli 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 ejeded by other vol-
canos more known 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 flioerl in the mafs, contain
feltfparSj cryftallized fhoerls, or chryfolites.
FeltfparSj garnets, and cryftallized fhoerls
are incorporated in the lavas of the volcano*
of the Eolian ifles, in a bafe of petrofilex,
horn-ftone, and fhoerl 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 v^rith a horn-ftone bafe abound in
feltfpars f. The iflands of Ponza afford
both granitous and filiceous laVas, accom-
panied wdth Ihoerls, feltfpars, and micas ;
and St, Flora in Tufcany is compofed of
granitous lavas f .

* Gioeni, ubi fup.

f See Chap. V.

I Dolomieu, ubi fup-

The

C 30J )

The produds of the Euganean moue*
tains, we have feen, are perfectly, fimilar.
The bafe of their lavas, w^hich is Ihoerl,
feltfpar in the mafs, pitch-ftone, horn-ftone,
■or petrofilex, is combined with feltfparj
cryftallized fhoerl, or <|uartzole 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 ancient fubterranean
fires, which have laid wafte a great part of
Italy and the adjacent countries, have had
their feat in thefe rocks ; and who can fay
to how immenfe a depth they may have
extended beneath the furface of the earth ?
I fay beneath the furfafce, becaufe, though
by the violence of volcanic fires large and
numerous maffes arife above the furface,
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

•v-oL, HI. X carbonatesg

( 3<=^6 )

carbonates, fteatites, arenacious flones,
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, unafFedied by the
fircj 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 of
that interefting country. But from fome
fpecimens which I received from fome
friends, and, among others, from Signor
Giovanni Arduino, and efpecially from
the converfations I had with him on the
fubjedl at Venice ; I clearly underftand
that the lavas found there have reck for
their bafe ; which rock is fometimes a
petrofilex, and fometimes a horn-ftone ; the
extraneous bodies contained within them
are fhoerls, feltfpars, and micas, ^ometirne!^
the volcanic rock is granitous,

I fhould

( 3^/ )

- I ' fhould wander beyond the limits I
have propofed to myfelf, fhould I proceed
to confider the nature of the ftony fub«
(lances which have been aded 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 aloioft all, rocks or com-
pound ftones. As therefore the fires of
volcanos extend to a prodigious depth,
as may be deduced from the vaft moun-
tains they raife above the earth ; it follows
that thefe rocks, befides conftltuting nu-
merous chains of very lofty mountains,
defcend to an immenfe depth, even in
thofe places Vv^here 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 costing, of
this globe ; the only part of it vvhicl^
man is permitted to examine ; and which
wg never could have obtained knowledge

X 2 Cf

( 3o8 )

of to fo great a depth, but for the Eery
tprrents 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-ftone. The former of thefe is
changed by the a(3:ion of the fire into a
vitreous lava, the equal to which I have
not feen among the produds of aray 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 palled immediately into glafs or
enamel.

The petrofilex, likev^rife, forms a kind
of general exception with refped: to the
Eolian volcanos. We have feen that
juany pf their lavas have the petrofilex

for

( 3^9 )

for their bkfe. This ftone almoft always
fufficiently preferves in them its primitive
charaders ; but it is accompanied with a
principle, if I may ufe the expreffion, of
fibrofity and expanfion in its parts, which
exhibits no obfcure fign of its having been
£t€ted 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 refpeft to their texture, grain, com-
padnefs, and fracture, fo exactly refemble
the moft perfed:ly charadterized natural
petrofilices, that they might be miftaken
for them, if we did not find that they have
pafTed into the flate of lava. This peculi-
arity, however, is not confined to the Eu-
ganean volcanos ; it likewife appertains
to thofe of the ifles of Ponza, as has been
fhown by M. Dolomieu in great numbers
of lavas with a petrofiliceous bafet. Thefe
lavas cannot but greatly excite our admi-
ration, as we find it impoflible to conceive,

♦ See Chap. XIH.

X 3 from

( 3'^o )

from the knowledge we have of our com*'
mon fire, hov\^ luch a flone can be liquefied
and flow without loiing one of its natural
lineaments.

Laftly, the lavas with a pitch-ftone 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 throw^n out a fmgk
fragment of them : and the fame obferva-
don may be made of the reft of the Phle-
PYXdiU fields. In Lipari alone, among all
the Eolian illands, I have found detached
and fcattered pieces, but which had rather
paiTed into the flate ©f 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 J to enquire whether it is to be
clafTed among the lavas, or rather whetheir
k has ever formed currents. We may be

* S^e Chap. XVir.

fatisfi'sd

( 3^1 )

fatisfied that it muft, as well as the pitch-'
Hones 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 iilands of Ponza, fpeaking of the
Vicentine lavas, he remarks, that he found
among them fome productions of pitch-
ftone, which he could not conlider as a
trufi. 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*
t'rom v/hich 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-
nean mountains, I did not find an atom of
thi§ earth.

* Notes on Bergmann,

X4 The-

( ^12- )

The Abbe Fortis affirms that he had
difcovered, in the pitch-ftone lavas of
Monte Brecalon, the evident tranfition of
|)etrorilex into pitch-ftone lava ; and on
comparing the analyfes of petrofilex made
by others, w^ith thofe I have made of three
pitch-ftones, it will be found that they
perfedly agree— ^with. no other difference
deferving notice, but that the petrofilex
iifually contains no iron, of which a very
fmall quantity was found in the pitch-ftones-
1 analyfed. *

As it ha-s been already fhown, tha!
pitch-ftones that are not voleanic and
thofe which are, are of the fame genus,
I find little difficulty In believing that
many of the latter are derived from the
former.

In all my refearches relative to the rocks
of the volcanos in the two Sicilies, 1 have
always been attentive to difcover at what
degree of heat they fufe in our common;
lire, that I might infer the axStivity of the

fubrerranean-

C 3^3 )

lubterranean conflagrations by which they
have been melted. I have proceeded in
the fame manner with refped to the volca-
nic rocks of 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 refradiory, not
even excepting the hardeft and moll corn-
pad petrofilices, which have formed cur-
rents. The feftfpars and micas, with which
the Euganean lavas fo abound, appeared
equally fufible.

The eafy fufibility of the feltfpars excited
in me fome furprife, v;hen I confidered the
infufibility which, if not conftantly, is very
frequently the property of the fame flones 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
were detached from their bafe, it cannot be
alleged that this bafe ferved as a flux. A dif-
ference fo remarkable, it feems probable, can
only proceed from the different, proportions

o of

1^

( 3'4 )

of the confiltuent principles, unlefs "^'t
cboofe to fuppofe that in the Euganean felt-
fpars, befides the elements common to that
{tone, there exifts fome" other which facili-
tates their fufion, though it is imperceptible
to the eye, the external appearance of the
fufible exadly refembling 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 v/bat has
been faid above. The adion of our com-
mon fire, therefore, deftroys in thefe volca-
nic products that primitive charad:eriftic
ftrudure which had been left in them by
the fubterranean conflagrations^. -

The bafaltes of Vulcano and Felicuda are
products of fire, and equally fo are thofe of
Monte Roflb, Monte Ortone, and Catajo ;
for they are integrant parts of continued
volcanic rocks ; which truth did not efcape

the

( i^s )

the acute obfervation of Sir J. Strange ari^
other difcerning naturalifts. It deferves re-
mark, likewlfe, that the trapp has taken a
prifmatlc 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
bafaltes 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 Vicentine
mountains, at Vefuvius, in the extinguifhed
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 ihall not enter
into this queftion, which indeed appears
to be precluded by the obfervations of the

Abbe

( 3!6 )

Abbe I*'ortis ; my only objed:, in fad, being,
in this ibort excurfion to the Euganean
mountains, to colled fome 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.

( 2>'7 )

CHAP. XXI.

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

7he perfeEl refemhlance of the effeEls produ-
ced by fame gafes of volcanos and thofe of
others generated hi lavas ^ and other fimilar
fubfanceSj ivhen re-7nelted in our common
fre^ tnay enable us to df cover the nature
of the former^ by invefigat'ing that of the
latter — Matrajfes of clay^ filed to a cer-
tain height with volcanic produSls^ expofed
to the f re of a chemical furnace^ and com-
municating with a pneumatic-chemical ap-
paratus prepared with mercury — Expert'
ments made in this tnanner on the fpotted
glafs of Lipari — Phenomena obfcrved
withijt the matrafs during ignition — No
gas appeared above the mercury — ■Kbulli-
pit fate in which the glafs was found

when

( 3'8 )

iM)'hen left to cool in the matrafs^ after haV'*
i?ig bee?i eight hours expofed to the fre —
No reafon to believe that the bubbles were
an effeSl either of the atmofpheric air in-
cluded in the int erf ices of the glafs^ or of
any perma7ient gas — ConjeEtiire that thefe
hubbies proceeded from the gaff cation of
the glafs itfelf occafoned by the vehemence
of the heat — Proof of this conjeBure in the
puref glafs of Lipar'i- — 'The breaking of
the matrafs in the frongef heat occafoned
by this gaff cation — Caife why the glafs
rendered gafeous does not pafs into the
pneumatic apparatus — Breaking of a third
matrafs by the viole?7t gaff cation of an
enamel of Ifchia— Enamel of Procida dur~
ing the gaff cation fublimedy and adhered
to the fides of the matrafs in the form of a
thin cruf^ and enamel points — Confirmation
of this in another matrafs^ ufng the fame
enamel — Evident fgns of this fublimation
In the fufioji of fome volcanic fubfances
placed in the furnace, in covered crucibles
— Reafon why this fublimation does not
appear in every e^periment-^^Black fa^i-

( 3^9 )
J^ous glcifs *which does not produce gas
in the furnace, but 'which produces it,
'Within matraffes, in ajlrong heat — Expe-
riments onjix other volcanic bodies^ which
produce little or no gas in the furnace, but
a confiderahle quantity in matrajfes, 'with'
' out any appearance of permanent gas- —
Conclufion that the hubbies and inflations of
'various fvzes, 'which "we fo frequently ob^^
ferve in the productions of ,volcanos, arc
not the effcEi of any permanent gas 'which
has a&ed on them, hut of an aeriform fluid
proceeding from the excefjive fuhtili%atinn
of thofe produdlions by tmans of heat —
Not but that volcanic produBs, cxpofed to
cur common f re, fometi^nes emit permanent
gas — Proofs, deduced from fa£fs on v
f mailer fcale, that this aeriform fluid, in
the deep receffes of a volcanic crater, being
abundantly mixed 'with the. liquid lava,
and flrongly excited by the fuhterranean
conflagtations, may, by its violent force,
raife the lava to the fummit of the crater^
and compel it to flo'w over the fides and
form currents,-^ Another proof of this faSi,

"which

( 3^0 )

^^hich renders probable the bypotbejis, that
this elafiic vapour^ colleBed in a large
quajtt'ity^ and Ji7idi?ig fome impenetrable
objlacle under the earthy may caiife earths
quakes y fitbterranemis roarings^ and burji
the fides of the mountains ^forcing the lava
to fow out — Improbable, however, that
this vapour is the caife of the fery hail
ejeBed by volcanos — Necefity of recurring
to other more powerful gafes to explain
thefe eruptions — The prefence of thefe dif
fere?tt gafes clearly indicated in fome vol-
canos— Probable, that in the greater and
more terrible ejeclions another agent much
more energetic concurs, that is, water,
principally that of the fe a, reduced to va-
pour—Connexion bet'ween burning volca-
nos and the fea — The fuddeii retiring of
the latter, in the vicinity ofVefuvius, at the
time of the mq/l terrible eruptions, probably
occafioned by great quantities of its waters
being abforbed in the caverns of the moun-
taiti — Experijnents and accidents vohich
prove the terrible nature of the explofions
q,nd detonations of volcanos^ in confequence

of

( 321 )

yf waters being reduced to vapour by their
co7iflagration—Knquiry whether water
.failing upon a ourning volcano 7nay be ca-
pable to pt^oduce es<!ploJions, as it is ce?-tai?i
it will if it injinuates itfelf 171 fj'om below) ^
and its vapours cannot otherwife obtaiti a
paffage out — Water falling upon oily and
boiling matters generates feeble explofions^
^johich feeins to favour the afirinative—-
Arguments for the negative deduced from
the effeBs of water poured onfome fnelted
fubjlanc-es, which are more analogous than
oily to the liquefied matters of volcanos —
No explofion or detonation occafoned by
water falling on cryfal liquefied in the
furnace— Cm'ioiis phenomena obferved in
this experiment — Similar effeEis produced
by letting fall the fame fiuid on iron or
copper i?i a fiate of fufion- — Kxplofions
and detonations in water^ as foo?i as it
touches the furface of melted tin or lead —
Thefe explofions greater ivhcfi the water
remains enclofed withifi thefe melted inetals
—Remarkable diverfities in thefe expert"
ments — Kxperiments on lavas melted in the
VOL. lii, Y furnace—^

( 322 )

furnace'— 'No explofion produced by pouring
"water on them^ njohen it is not ititroduced
within them — The explofion the Jlronger
the ?nore the water penetrates into them —
The refnlts the fame when fea^ivater is
ufed injiead of frefJo — Conch fion, that
'water is incapable of producing eje&ions
ivhen it falls on the burning craters of
volcanos ; but that it mtfl produce very
violent ones when it penetrates into them
from below or by the fides — The different
permanent gafes difcoverable in volcafios
feem alone to be the caufe of the more mo-
derate and fmaller eruptions — The fymp-
toms^ and inceffant ejeBions^ of Stromboli
cannot be caifcd by the evaporation of
water ^ nor by that of the liquefied lava^
but mufl depend on the aBivity of forne
permanent gafes — Enquiry whether this
gas be hydrogenous — That fuppofitio?i re-
jeSied — It cannot he fuppofed to be atmO"
fpherie air — The hypothefis ivhich has
recQurfe to oxygenous gas to explain the
phenomena of the volcano of Stromboli^
feems leaf improbable,

HAVING

( ?>'^2> )

JlIaVING finifhed the defcrlptlon of the
products I obferved in my excurfion to the
Euganean mountains, I might confider my
volcanic travels as concluded ; but agree-
ably to the plan I propofed to myfelf in the
Introdudtion 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, glafles
and enamels. 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; fince, by the adion of the fame
gafes, we frequently obferve fimilar pheno-
Y a mena.

( 324 )

tnena m the furnace. But, in the prefent
age, in which naturalifls and chemifts are
fd earneftly employed in analytical re-
fearches relative to the nature of aeriform
fluids, it is not fufficient to aflert and prove
the prefence of gafes in liquefied volcanic
products ; it is liketvife 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 interefltng obje£t pointed out
in the Introduction, and which well merits
difcuffion, is the enquiry relative to the
activity 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 fubjecSted to fufion, it appears
to be proved that this a<51:ivity may not be
very great ; as a not very ftrong common
fire is fufficient to produce the fame effeds.
From thefe experiments we certainly ac»
quire fome knowledge of which we were

not

( 3^5 )

not before in pofTelfion ; but I do not con-
lider the problem as undeniably foived ;
fince to thefe facls 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 Ihall impartially confider th^ 1
weight of each, and afterwards give my
iincere and unbiaffed opinion.

Thefe two fubjed:s I fliail proceed to
confider in two chapters, between which
I fhall infert a very fhort one, containing
an account of a chemical difcovery made in
the courfe of my experiments. Thefe will
conclude my enquiries relative to thefe
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 mean£ to difcover the nature of
Y 3 thefe

( 32^ -)

thefe fituds. I refolved, ia confequence, to
fufe within matralTes various voicanic pro-
ducls ; fuch, 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
with mercury, in order to colled; and exa-^
mine the gafes which fliould be difengaged,
by the adion of the fire, from the liqueiied
fubftances. The matrafies 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 vefTels in a glafs-houfe.
They had a fpherical bottom with a long
neck, and were of the thickneis of fix full
lines. I tried them by plunging them into
"water and blowing flrongly into them,
when I did not find the fmalleft 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
liifTrng found that might indicate the efcape
of air. 1 repeated thefe proofs, likewife,
after I had made my experiments, and thus

was

( 32? )

was certain that the fluids I found In the
veflels could not have entered them from
without. To the neck of the matraffes 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 collect it.
Such a liquor was, in fad, feparated ; and
I found it to be of a nature which I never
could have imagined. I Ihall defcribe it in
a diftin<3: chapter, to prevent the confound-
ing of objedis totally unlike in one difcuf-
fion.

The firft product on whic'fl I made my
experiments, was the fixth fpecies of the
glaiTes of Lipari ; that which I have de-
fcribed as having a black ground fpot-
ted with 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

( 328 )

the volcanic fires. The matrafles were of
that capacity, that the twelve ounces of
every produd: 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. nor
extinguifh that flame, nor render it brighter,
but left it precifely as it was in the atmo-
fphere ; confequently this fluid muft be
Gonfidered as common air, that is, a portion
of that contained in the vefl!els ufed in the
experiment. That fuch was the fa6l, I was
ftill more convinced by fubje£ting this fluid
to other experiments. Another fmall quan-
tity of fluid afterwards colled:ed from time
to time on the mercury, which I examined

as

( 329 )

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

Dire6ting ray eye along the glafs tube
luted to the neck of the matrafs, I could fee
the bottona of that veflel by the light of the
iire 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 confided of tumours that rofe
extremely flowly from the furface of the
fufed glafs, and funk again as flowly ; and
fome of which, having attained their great-
efl dilatation, burfl. 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

( 33^ )

When the matrafs had coded, I broke i£
lengdiwife, and obferved the following ap-
pearances : The glafs when fufed had iiiied
tw^o thirds and more cf the body of the ma-
trafs, to which it was ftrongly attached, and
formed in the upper part a plain farface,
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 was 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 crofTed it with
the two ends adhering to its fides, and
\Thich no doubt was produced by the vif»

cofity

( 331 )

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 fay5
to the naked eye, becaufe, with the lens,
the folid parts likewife 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, which,
in fad, is the principal obje<St of our prefent
enquiry. It feems undeniable that thefe
muil have been produced by an elaftic
fluid, which penetrated the glafs when in a
flate of fufion, and compelled it to dilate
in that manner. This fuppofition I have
always made in the courfe of this work,

when

{ 33^ ) -
when I have fpoken of volcanic produds
become ebullient within the crucibles, and
alfo of thofe which have pafTed into fuch a
itate by the adion of fubterranean fires ;
nor do I conceive that it will be contro-
verted hj any perfons. Whoever has feen
fuch produdions, will admit that this fup-
pofition is fuppcrted by the flrongeft evi-
dence.

But what may be the nature of this
fluid ? We cannot imagine it to be atmo-
fpheric air whiph occupied the pores of the
pulveriftd glafs contained in the niatrafs,
fmce this muft have been expelled at the
very beginning of the fufion ; wherer\s the
tumours on the furface of the liquid glafs
were produced in the ftrongefl: heat of the
fire, and continued as long as it remained 5
an inconteftable proof that, then, the fluid
in queftion copioufly invefted and agitated
the vitreous mafs. This fluid, likewife,
cannot be called permanent, like the differ-
ent aeriform gafes, fince, were it fo, it would
have colleded on the mercury. I therefore

began

{ 333 )

began to fufped that it muft be an evapo-
ration of the glafs itfelf, which, in confe-
quence of the vehement heat, pafled from
the ftate of fluidity to that of vapour or gas,
and continued fo while the degree of heat
remained tlie fame. Thus we fee metals,
afted 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 foiid
ilate, the flate of fluidity, and the aeriform
flate J thefe three diflferent Hates 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
lefs violent, was incapable of preferving it
in a gafeous ftate.

To afcertain the truth of this conjedure,
it was necelTary to have recourfe to other
proofs. I, therefore, proceed to the fe-
cond experiment, in which the circum-
ftancea v/ere the fame as in the former ;

except

( 334 )
fejicept that, during the laft four hoiirs^
the fire was violent. The glafs on which
I made this experiment was the fifth fpe-
ties of the glaffes of Lipari ; which is thd
moil perfed and the pureft glafs afford-
ed by the ifland. The refults were as fol"
low i

TJie fmall quantity of air which rofe
above the mercury during the ignition was
found to be purely atmofpheric. Aftei*
half an hour's violent fire, I perceived,
through the glafs tube inferted into the ma-
rrafs, the vitreous mafs beginning to rife in
tumours, which prefently rofe fo ftrongly
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 matraifes. 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 iifue through the

fradure.

( ^35 )

fracture. I therefore caufed the fire to be
extinguiihed, and^ after the matrafs had
cooled, examined it within and without. I
found, on one fide, an angular fiflure, 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 iifued from the matrafs. Within was
an oval bubble, occupying two full thirds
of the body of the matrafs. This faft ap-
peared to me of confiderable importance^
It is evident that this bubble was the effed;
of an aeriform fluid, which by its expanfive
force had not only produced that vacuity;
; but broken the matrafs by ftriking forcibly
againft its fides. It is iikewife 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 y/as full of minute cavities.

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

,f. chia.

{ 33^ )
©Ilia. KerCj therefore, the ftrohg gafiflcg-
tion of the enamel, by the violent energy of
the fire, had produced a vacuity which oc-
cupied more than half the matrafs, forcing
up the enamel, and compelling it to afcend
through the neck j breaking at the fame
time the fides of the matrafs.

In a fourth experiment I made ufe of an
enamel of Procida. During a continuance
of eight hours in the fire, I obferved it at-
tentively, but could not perceive any figo
of ebullition. I afterwards broke the ma-
trafs, and found that, notwithftanding it?
complete fufion, and that it was in every
part full of bubbles, the bubbles were m.
«:^eneral fmall. No' particular gas appeared
^bove the mercury.

Examining, afterwards, the internal fide^
of the matrafs, above the hardened enamely-
I made an obfervation that appeared to me
important. A great number of very minute
globules of the fame enamel adhered, her©
and there, to the fides, at the diftance of

half

{ m )

half an incli, an inch, or two inches, froiii
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 rifeh to the
places where the traces of it fo evidently
appeared ; fmce then the fides would have
been varnifhed 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 perfectly free
from any appearance of enamel, as they
were before the experiment 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 ' v/hich

{ 338 )

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

A doubt however remained, which it was
neceffary 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
hav^- 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 matrafles was a confequence of
their vaporifation, determined me to make

a general

( 339 )

a general revifion of the various crucibles I
had before made ufe of in the furnace, and
which had contained veficular volcanic pro-
duels ; as 1 had not before examined them
"with a view to this obje6t, believing that
the veficles or bubbles were caufed by fome
permanent gas. There were not a few, to
fay the truth, the internal fides of which
exhibited, above the fufed produ^, fmall
drops of the fame fubftance : but it was
eafy to perceive that thefe were not colleded
there by fublimation ; but were thrown to
that iieight by the inteftine motion of the
products in fufion. There was, however, no
crucible which prefented that thin coatingj
or that aggregate of infinitefimal globules,
obfervable in the laft experiment, and
which manifefted an evident fublimation of
the fufed fubftances. This, indeed, did not
furprife me ; as the crucibles were of a
cylindrical, or inverted conical form, and
open at the tep ; fo that the particles which
might fubli me met with no oppofmg body
to detain and collect them.

Z 2 I, there-

( 340 )

I) therefore, refolved to endeavour to af-
certain whether this fubUmation took place,
likewifcj 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 refpedlive
matters fufed in the three crucibles. But
nothing fimilar was apparent in the other
three crucibles. The former of thefe fads,
which is pofitive, is a new and luminous
proof of the gafificationof volcanifed produc-
tions ; and the latter, which is negative, no
proof to the contrary ; fince, though every
one of thefe fixteen produds were ebullient
within the crucibles, and therefore, from
what has been above faid, there is the ilrong-
eft reafon to believe they were rendered fo

( 341 )

:by internal vaporifation ; it is not neceflary
that they fhould fubllme with evident ex-
tern?^ indications ; this depending on the
nature of thefe fubftances ; fome fubliming
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 fublimation ; though I
have no doubt that it would have been ob-
tained Hkewife in them, had the fire been
fufficiently increafed.

But to return to the experiinents I was
relating. After having made thofe now
defcribed on volcanic glaffes and enamels, I
proceeded to fubje£t to the fame proof a
fadiltious glafs j 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 obferved that this
Z 3 glafs

( 34^ )

glafs in tKe 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 fad:, however,
is, that after remaining the ufual eight hours
in the furnace, the matrafs having been
broken, the ebullition and exaltation ap-
peared to have been fuch, that the glafs had
rifen 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 Ihining 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 underilood and fatif-
fadorily explained by the theory of the ga-
fitication of the fubftances hitherto treated
of. The heat of the furnace was fufhcient

to

( 343 )

fufe this glafs, but not to convert it into
gas. The chemical furnace, being more
adive, rendered it gafeous. Hence arofe
that violent tumefadion ; though the adion
of the fire having afterwards diminifhed,
the glafs confequently pafled 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
colleded, more or lefs, above the mercury :
but nothing was found except common air,
as in the other experiments.

Hitherto I had only ufed thofe volcanic
produds, which, in the furnace, are filled
with bubbles more than others ; being de-
firous to obferve whether the fame effed
would take place in the matraffes, 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 flate the qua-
Z 4 lities

( 344 )

llties of the fubftances I ufed, and the re-
fults obtained.

Thefe fubftances were fix in number : a
lava with garnets from Vefuvius ; another,
which, when 1 vifited that volcano, had re-
cently flowed ; a lava of Vulcano, invefted
with a cruft of enamel ; the lava continu-
ally ejected by Stromboli ; the lava which,
in 1787, ilTued from the higheft crater of
Etna ; and a folid pumice of Lipari. I
have already defcribed each of thefe pro-
duifts, when treating of their refpedive vol-
canos.

After they had been espofed to the fire
eight hours, in matraifes, nothing was foun4
to afcend above the mercury but atmofpheric
air, or a portion of that the vefTels conr
tained. Thefe fix products, therefore, af-
forded no indication of any permanent
gas ; but they evidently fhowed that they
fiad pafled from the ftate of liquidity to
that of a ftrong gafification, from th?

quantity

( 345 )

quantity and fize of the bubbles they con-
tained. This Is confequently another and
a moft convincing proof, that a greater
gafification of ftony fubftances may be ob-
tained in a very ftrong heat than in a
v\^eaker.

From thefe ten experiments I conceive
myfelf fufficienlly v^r^rranted to conclude,
that thofe bubbles and inflations of various
fizes, which we fo frequently obferve in
the produces of volcanos, are by no means
caufed by the adtion of any permanent gas,
but by that of an aeriform fluid produced
by the exceflive attenuation of thofe fame
produ(5ts in confequence of heat.

I do not know that fimilar experiments
have been made by any other perfon gk->
cepting Dr. Prieftley, who defcribes three,
vv^hich I think proper to be mentioned here,
as they differ fomewhat from mine. This
naturalifl:, having fufed in a fand-ftone re-
tort 4^ ounces of Iceland lava, obtained 20
ineafures of air, the half of which, about the

beginning

(' 34<^ )

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

£~ ounces of lava of Vefuvius gave 30
meafures of air ; the firfl portion of which
Ihowed 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 refidue, when it becarne
cold.

Another ounce of lava, of the conflft-
ence of a hard fl;one, gave only 3^ 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 naturalift
infers, that it is probable that the true lavas
^0 not afford much air 5 which, however,

according

( 347 )
according to him, mull depend on the de-
gree of heat to which they have been ex- •
pofed in fubterranean fires *.

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

But fuppofing they adually were fuch,
if we oppofe our ten proceffes to the two
of Dr. Prleftley, the confequence to be de-
rived will be, that volcanic produfl;s are not
always deftitute of permanent gafes ; which
deducTdon will be found perfe£lly to agree
with obfervations 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 produds expofed to our common

t Experiments and Obfervations on Air, Vol. IV.

fire.

( 348 )

fire, and, confequentlyj thofe fo extremely
iimilar 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 a£ts in the eruptions
of volcanos. 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. 1 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 produd:s which mofl inflate
and boil in the fire. After fome hours, I
obferved that the liquid matter began flowly
to rifej and afterwards to rife higher until

( 349 )

it at laft overflowed the edges of the cmcU
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*
du£t 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 glafTes
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, v^hen coUeded 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
I may fo fpeak, in miniature, in the two

matraffes

( 35^ )

Jnatraftes broken by this fluid from its exii^
berance and the refiftance it met with. I
afterwards made in the furnace fdme expe^
riments more decifive. I caufed three ma-^
traffes to be made, on purpofe, of clay,
the fides of which were an inch thick, and
the belly, which I more than half filled
w^ith a cellular lava, four inches and three
quarters in diameter ; the neck projed:ed
in part from the furnace. At the end of
eleven hours the three matraffes were broken
in the belly, Vv^ith feveral fiffures, through
which the lava iffued. Having afterwards
broken up the matraffes, 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 fufficient to keep it in fufion.
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 ; bu£
iofinc; there its fiuiditv from the cold, it could
advance no further ; and, its inflation in-
creafmg from the vehemence of the heat,

the

( 35J )

tlie matrafs at length v/as forced to openi
I find, therefore, no difBculty in believing
that fuch a vapour may produce fimilar
effeds, on a larger fcale, within the earth,
when it meets any obftacle to its expaniion,

I cannot, however, Co eafily admit that
the fame vapour is the caufe of the fiery
hail or ejections of volcanos, as the break-
ing of the matraffes happens without the
leaft noife, and without the ejed:ion or fcat-
tering of the contained matter. 1 atten-
tively watched two matrafles 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 matraifes, a£i:s neverthelefs very flowly ;
w^hereas the agent which hurls the burning
matters into the air from the volcanic
mouths mufl adt with the utmoft rapidity
and violence.

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

Modern

( 3^^ )

Modern volcanifts have fuppofed tliat thefe
are various gafes, which, endeavouring to
obtain a paiTage through the liquid fub-
ftances in which they are enveloped, force
them impetuoufly out of the crater, and
fometimes to an enormous height. The
prefence of thefe gafes is certainly not ob-
fcurely manifeiled by the hiflrng founds
that are heard during the raging of volca-
nos, aS' has been obferved of Vefuvius,
which, from its vicinity to Naples, is the
volcano that has been moll attentively exa-
minedi. Similar hilling founds I likewife
obferved at Stromboli, of the eruptions of
which volcano I fliall prefently have occa-
fion again to fpeak.

But what is the nature of thefe different
gafes ? 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 impoflible, from
the manifeft danger there would be of fall-
ing a vidlim to fo imprudent a curiofjty.
We can therefore obtain no knowledge of

them

( 353 )
them but by an indirect way, that isj by
obferving the gafeous fubllances which
arife from volcanos when they have return-
ed to a ftate of tranquiUity. If v^^e perufe
the works of writers on this fubjed:, we
ftiall find feveral of them named j fuch as
hydrogenous gas^ fulphurated hydrogenous
gas, carbonic acid gas, fulphureous 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 ejediions, another more
powerful principle comes in aid, which is

* From the agents which by their expanfive forc(j^-
produce the eru(Slations of volcanos I do not mean to
exclude caloric, which fometimes mufl necetTarily co-
operate ; that is, when in the volcanic recefles a greater
quantity of this fluid Is fuddenly difengaged than can
eafily find a paflage through the pores of the furround-
ing bodies. Then, as Lavoifier has obferved, caloric
will a6l Hke other common eiaftic fluids, and overturn
every thing which oppofes it. Except in this circum-
flance, however, I do not fee what immediate adlion it
can have in volcanic eje<Slions-

VOL, III'. A a water,

( 354 ;)

%^ater, principally that of the fea. It
would be fuperfliious to fhow, fmce it is
generally known, that the volcanos fcattered
over the globe, and which at prefent throw
out fire, are either furrounded by the fea,
or at a fhort diftance from it ; and that
thofe which have long iince ceafed to bum
are, for the moil part, at a confiderable di-
ilance from it. The confervation, and we
may iikewife fay the origin of thefe fubter-
raneaa conflagrations, have therefore a
fecret relation to the waters of the fea.
There is little doubt but thefe waters com-
municate by fecret paiTages with the fpa-
clous caverns and profound depths which
exift, certainly, in burning mountains ; and,
though we are not able to difcover this im-
mediate communication from without, it
is fiifficiently vifible by its effeds ; I mean
tlie fuddea retiring of the fea at the time of
the moil violent eruptionSj 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-

( 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 periihed. An-
other fimilar took place in modern timeSj
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 circumflance," Steller5-pn
his Obfervations on the Volcancs of Kam-
fchatka, remarks, that the greater part of
earthquakes happen at the time of the equi-
noxes, when the fea is mofl 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 muft caufe prodigious ex-

A a 2 plofions.

plofioiis, and detonatioas, far more violent
than thofe occafi-oned by the elaflic gafes
before menlioned. Thus, if a cannon, after
having been fiied feveral times, be fpunged
with a wet rammer which too exactly 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
fiie 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 expofcd
to a ftrong fire,^ it will foon burft with
;^ioud noife, in the lame manner as if the
explofion had been caufed by gunpowder*

But nothing, in my opinion, more aptly
£hows the nature of the deftrudive explo-
lions which volcanos may produce by the
evaporation of vv^ater, than the fatal acci-
dents which fometimes happen in confe-
•quence - of pouring ■ melted metals into
moiilds not fufficiendy dried. An account
,Qi eae of this kind may be found in the

fourth

( Z51 )

fourth volume of the Memoirs of the Aca-
demy of Bologna, which I fhall here briefly
ftatc, as it is particularly applicable to the
prefent fubjedl. A bell of a very large lize
was to be call: at Modena under a fpacious
portico. The mecal was melted, and was
let flow, through a fniall channel, into the
earthen mould, which was at a little diftance
under the pavement. But at the moment
the melted metal reached the mould, fuch a
violent explofion took place, that the metalj
the mould, and a great quantity of earth,
were thrown up with inconceivable vio-
lence. The furnace was blown 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 byftanders were
killed, others feverely wounded and hurt,
and all overwhelmed with dread and con-
fternation. Such dreadful effedis were pro-
duced by a little moifture being left in the
earthen mould, through the inattention of
the workmen. We may hence conclude
A a 3 what

C 35S )

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

Here a qneRion naturally arifes, which
it may not be unufeful to difcufs. It can
admit of no doubt, that water infinuat-
ing itfelf under the burning matter, and
fuddenly reduced to vapour by the extreme-
heat, if it can obtain no paffage, will caufe
the moil terrible eructations. But what
effed; will it produce fhould it fall upon the
fire, fuppofing it either fea- water or rain ;
for the latter may eafily penetrate, through
the pores and fifiures of the earth, to the
volcanic furnaces ? If we attend to feme
experiments, we fhali be inclined to fup-
pofe that the evaporation of the water in
the latter cafe will produce the fame effect
as in the former. Thus, if we throw
drops, of water on an oily and boiling mat'^
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

explofiou

( 359 )

cxplofion and fhaking of the containing
veflels.

But other fads, more confentaneous to
the nature of volcanos, prove the contrary.
It is well known to all mineral ogi lis, 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 Dellandes,
relative to the efFed:s of water poured upon
mfelted glafs contained in capacious cru-
cibles, in a glafs-furnaee, are equally de-
ferving attention in themfelves, and appli-
cable to the prefent queftion. I ihall give
a brief abftrad: of them. A glafs of water
having been thrown on a quantity of melted
glafs, the water faddenly formed a globule
without producing the leail: found : it slC-
fumed, or feemed to alTume^ a red colour,
fimilario that of the crucible and the melted
glafs. It roiled on the fur face 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 dimininifhed, 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, which 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 fubjed:, whom I
found fo well acquainted with the fad: that
he offered to pour as much water on melted
glafs as I pleafed, alTuring me that not the
fmalleft ill effed: was to be apprehended. I
perceived, therefore, that this was one pf
thofe phenomena which are publifhed to
t^e world as new, and which, in fad, ar^
fp to the learned, but have been long well
Jcnpwn to many of the vulgar,

I began

( 3^1 )

I began my experiments with pouring
iix ounces of well-water into a cylindrical
clay veflel, about two feet in diameter,
which had for fifteen days been nearly full
of melted factitious 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.
Tiiefe globules rolled about, gradually di-
minifhing 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 ebullitign, I repeated this experiment
by emptying into the veffel 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 firfl the globules, moving as
ufual on the furface of the melted glafs,
ihowed no (ign of ebullition ; but this, a
fgw inftants g^fterwards, became vifible, in

thofe,

(: 3^3 }

ihofe,, atleaft , that were nearell to me ; wlieiKc
it may be concluded that the fame happeriCcl:
in thofe at a, greater diftance. They boiled •
akid fwelled perceptibly, but did not caufe
th© kaft found ; the water being in a fpaee^
if not deprived of- air, at lead containing' -
©nly fuch as mull be highly rare-fi^d^'
Theyj however, as' iii^ the former ek-periv'
jiient, eontinuaiiy di-nVi^iihed isi-iize, -and^
after about four minutes, ' eiitir-ely difap-'
peared. During their ebullition, no'fi^o
of any vapour was difcoverable around-
ihemt.

It would be fuperfluous prolixity to de-
fcribe feveral other experiments which I
made with ftill greater quantities of water^
no difference being difcernible in the re-
fults. I very attentively obferved whether
the water aimmed a red colour, but faw no-
thing like it: this miftake mufl: have been
occafioned by the rednefs of the hot glafs
furrounding the w^ater.

Gn comparing thefe fads with thofe ob-
ferved

{ 363 )

ferved by Deflandes, I find them perfectly
accord, except that the ebullition, which
certainly takes place, was not obferved by
him. When we proceed to apply them
to volcanos, with refped: to the falling of
water on their burning mouths, we fhall
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
fqme other experiments, both on diiierent
metals and lavas in fufion. I made ufe of
iron, copper, tin, and lead. With refpe6t
to the firft, I employed filings of it, to faci-
litate its fuiion ; as I have already remarked
in the Introduction 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 j and I never
entirely filled them with metal, that there
might be room to pour on it a fufficient

quantity of water,

"j

After

C 3% )

ter the iron had remained twenty-
four- hours in thfe furnace, and was femi-
fufed, I let fall a few drops of water on it/
They at fifft remained motionlefsj without
apparently diratnifliing in bulk ; but they
foon after began to leap abotrt' and boll,
wafting away, till, in lefs than a miraife,'
they difappeared. When I poured on more
water the eiiedis were the fame? only the
ebullition was more fenfible, becaufe it was
|)roportioned to the greater quantity of
water.

Leaving the iron in the fumacfi, J, after
le¥en hours more, repeated the experiment,
having firll removed the crucible into the
cold air. I threw on the iron a flight
fprinkling of water ; but this in an inilant
difappeared without 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 fliort time it
entirely evaporated.

The

Tiie rednefs of the iron was now foniew=
what obfcured ; and I availed rayfelf of t3i^
circumftance to drop more water oa 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 fuflicient for me
to repeat this experiment twice m.ore wdtii
the fame effed:.

Copper in the furnace Vv^as completely
fufed. I made the fame experiments on it,
and with the fame circumftances as on the
iron, I omit defcribing the refults, as that
would only be to repeat exadly 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 fuflieient for the fa«
fion of thefe metals. But I foon perceived
that the confidence with vs'hich I had mad-e
my trials on the iron and copper, muft

not

( 366 )

not be continued with the lead, and ftill
lefs with the tin, on account of the violent
explofions excited by their touching the
w^ater. I made a great number of different
experiments on both thefe metals ; but, for
the fake of brevity, I fhali 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 Vv^as obfervable.

Approaching as near as this dangerous
experiment would permit me, and attentive*-
ly watching the progrefs of it, I obfervedj
that as -often as the drop of w^ater touched

the

( i^1 )

ih-e metal, the latter, by its fluidity, became
in motion. I iikewife remarked that, at the
fame time, a momentary cavity was pio-
duced in its furface, from the fall of the
drop, efpecialiy if it fell from any height.
It then occurred to me, that it might be
poffible that the explofion and detonation
might be the effe<^ of the water fmking
into the cavity, and being in part -confined
ia the melted metal ; where, paffing fuddenly
into the ftate of vapour, and finding no
room for its dilatation, it impetuoufly forced
out the metal. But this fuppofition did not
accord v>?ith the fad:. Had this been tb^
cafe, if the drop had touched the melted
tin vs^ithout linking the fmall cavity, it
would have caufed no explofion ; which
muft have been the louder and more violent
the deeper the cavity, v^rhich would then
have contained more water. I, therefore,
firft let fall the drops of water on the tin
from a very fmall height, and afterwards
from one of five or fix feet ; but I found
ao fenfibie difference^ either in the explo-

fioia

( 368 ) ,

fioii or ejedlons. The eifed: defcribed, k
may, confequently, be concluded, was pro-
duced merely by the fimple contad: of the
water and the tin.

I had, befides, fufficient proof that the
water, when included within this melted
metal, caufes ejections much Wronger 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 perforadoil
through the cruft that had gathered over it,
which was ftill 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 the cruft
had produced a vacuity between it and the
melted metal, which admitted the water,
but was muck too confined for its expan-

fion

( 369 )

fion when reduced to vapour, which, by-
its elafticity, caufed the violent efFed:s that
followed.

When the furface of the tin w^as cooled
and confolidated 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 aflign
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 ceafe, though I conti-
nued the fall of the drops, which, when
they reached the metal, only boiled and
evaporated. But what muft appear moil
extraordinary was, that after three or four
drops had produced no explofion, others
which fell immediately after again caufed it.
Nor m_uft we imagine that the failure was
occafioned by the water falling not imme-

VOL. III. B b diately

C 37° )
diately on the tin, but on the pulverulent
pellicle with which it is invefted by oxyda-
tion, fmce I carefully removed it as oftea
as it was formed.

Melted lead exhibited the fame appear-
ances with the tin, and fimilar irregularitieSy
except that its explofions with water were
not fo frequent, nor, as it appeared to me,
fo flrong.

I fhall not here enquire why the water
in the furnace exhibits no evaporation of
any kind, nor boils till after fome inftants j
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, Vv'hen 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 fa bj eel. It ap-
pears to me preferable to proceed imme-
I diately

( 371 )

diateiy to relate what I obferved in lavas In
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 firft I ufed were of that fpecies
which in the furnace become but little po-
rous. The water, when poured upon thefe
in a ftate of fufion, for fome 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 bad 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 refpedt
to their cauiing no explofion with water.

B b 2 I next

( 372 )

I next proceeded to the lavas filled witii
pores and bubbles ; but here more caution
was necelTary. In one of them, two large
bubbles appeared perforated on one fide.
On pouring the water into the crucible, il
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 frad:ure
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.

5 I con-

( 373 )

'I concluded thefe experiments with the
following : Having fufed a lava in a capa-
cious receiver of clay, I perforateid it ob-
liquely from 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. XXI II. that the lavas v.'hich are moft
eafily fufible, and which are inflated and
overflow the crucible, forming a ftream
down the fides, retain, nevcrthelefs, fo
great a tenacity in their parts, that they are
with difficulty pierced, and that the cavity
made by fuch perforation remains entire
but a very fhort time. I refolved to in-
troduce water into this cavity ; but as the
experiment was dangerous, 1 removed the
receiver from the furnace into a court-yard,
and poured in the v/ater by means of a
long tube of iron, which reached the vefTei
through a hole in the door that flmt in the
court-yard. As foon as the water 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 While

( 374 )
While making thefe experiment's, I wiHi-
cd to fatisfy my curiofity relative Xo another
particular. Hitherto I had ufed frefli vsra-
ter from a well : and I wifiied to afcertaia
Vv'hether there was any difference in the
efiedis produced by water from the fea ;
fince it appears highly probable that. -this.
water, by entering among the fires of voU
canos, is the caufe of their moft terrible
erucca-tions. I, therefore, caufed fome to
be brought, in clofed vefTels, from the
neighbouring gulph of Genoa ; but, when
I made ufe of it in firailar 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 expiofions ; but that the 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 :

( Z7S )

dilatation ; or when it infmiiates itfelf late-
rally among the liquefied matters ; of which,
we have a fatisfadtoiy proof in the explc
fion of the lava, violently forced from the
containing veffel, on the introduction of
water into a cavity made in it.

Though, from the fa<f!:s now^ adduced,
there is the utmopL reafon to believe, that
water changed to vapour, by the incredible
power it acquires, is extremely v/ell adapted
to produce the great volcanic eruptions ;
and, by the fudden 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 ejediions ;
as, to produce thefe, the different permar
nent gafes m.entioned 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 Stromboll*
In Chap. X. we have feen that the fymp-
toms of that volcano confift in an ebullition
B b 4 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 ejection took
place ; • that this was immediately followe4
by a finking of the lava to a certain depth,
to which fucceeded a new rifmg of the
fame, with like inflations and tuuiors that
burfl with fnnilar eje<3:ions and explofion ;
and that in this aiternatioji confifted the
adion of that vplcariQ,

i have already fuppofed that thefe tumors
are caufed by an elaftic fluid imprifoned
within them, which endeavours to obtain a
pajTage, and at length fiuds one, by burfting
the tumors and forcing up their fragments
to a confiderable height ; and this con-
jediure I then thought extremely well-
founded, and am ftill of the fame opinion.
It only remained to enquire what might b^
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
pf volcanos. From the obfervations I made

on

( 377 )

ipa die rpot, I was fufficiently convinced
ihat the fluid contained in the tumors
could not be derived from the evaporation
of the lava, fmce this evaporation (v^^hich,
from the fafts adduced, cannot be denied)
was, indeed, fufHcient to burft them, but
not to produce the ejections continually
pbfervable. Nor can we attribute them to
^evaporated water, as this would not have
ideferred its detonation when included in
thofe bubbles till it had reached the furface
of the lava ; but the explofion and ejed:ion
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 pafTed into the Hate of vapour, it muft
be manifeft that every eruption would be
jnuch rnore violent and loud. We muft
therefore conclude that the fluid in quef-
tion is a permanent gas, and probably one
pf thofe which are difcoverable in volcanos
^vheujin a fl:ate of tranquillity, they are ac-

cefllble,

( 3/8 )

Geffible, fuch as the carbonic acid gas, Iiy-*
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, coqjedured that its adtion
was caufed by hydrogenous gas. He fup-
pofed that the internal fire might difengage
this gas from the matters exifting near, but
not imm-ediately touching, the volcanic fur-
nace ; and that this gas, by fabterranean
paiFages, might reach the principal cavity
in which the conflagration rages, and there
fuddenly take fire.

This hypothefis, which that judicious
naturalift has propofed only in the fhape of
a doubt or conjedure, 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 refped to Stromboli, it cannot be
maintained when we cpmpare it with the

fads

( 379 )

fa^ts obferved. For, in the firft place,
though this gas has the property of rifing
in flame, it has alfo that of extinguifhing
fire placed tvithin 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
thfe 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 vlfits
I made to that volcano, I obferved that the
ftrongeft detonations were not louder than
the found of a verv 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 almoil at one inftant, mull

caufe

( 3^0 )

caufe a much ftronger detonation I But
the proof that admits of no reply, or rath§r
the abfolute demonftration of the infufii-T
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 leaft ap-
pearance of the feebleft 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 th^
crater.

> Compelled, therefore, to abandon this
explanation, it occurred to me whether atr
mofpheric air might not poflibly produce
the phenomena in queftion. I confidered,
however, that, before this hypothefis was
admitted, it would be neceiTary to Ihow
that the atmofpheric air had free accefs
from without the mountain to the volcano ;

that

( 38i )

that It iafinuated itfelf into the body of the
lava ; and iflued out upwards, cauling the
inflations, ejedions, and detonations. As
to the poflibility of its entrance to the moft
internal recefles, containing the melted lava ;
it feemed to admit of eafy proof from the
cavernous ftru^lure of volcanic mountains.
But how this air could be fufficiently pow-
erful to iniinuate 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 eaiieft palTage, which would 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 muil lufFer, it
would penetrate it extremely rarefied, and

be

( 3^2 )

be incapable of producing the explofiong
eontinuallj obferved at Stromboli.' I omit
feveral other objed:ions, as 1 think thefe
two are fufficient to demonftrate thfct 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 conjediural ? May not
the phenomena of this volcano be attributed
to the action of oxygenous gas ? On the
one lide, it is well known that the fulphate
of iron and the fulphate of alumine afford
this gas in abundance, when a6;ed on by a
flrong fire ; and, on the other, it is equally
certain that thefe two falts are copioufly
produced in volcanos. They may, there-
fore, in the profound receffes 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, burfling and
throwing up the fragments of the lava,
from its expanfive force being greatly ia-
creafed by heat. The ejedions- will be
great, fmall, or moderate, according to the
different quantities of this gas colleded and
difengaged.

Againft this hypothefis two obje<51ions
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 we know that it is with difficuky
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 objed;ion is, that the burning
lavas a£l;ed on by this gas would be con-
verted into a glafs, or homogeneous enamel ;
whereas the lavas continually thrown out
by Stromboli, befjdes that the bafe of the
primitive rock is fufficiently recognizable in
them, ftill preferve their fhoerls and feltfpars
in their original ftate of cryftallizatlon.

Both

( 3^4 )

Both thefe objedions, however, will, if!
my opinion, be found to have little weightj
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, with carbonic acid gas,
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 gratly weakened^
and the a6iion of the fire be prevented from
being fo violent as to deflroy the characters
of the primitive rock.

This hypothefis, however, as I have faid,
I offer only for examination, and fhall be
very ready to rejedl it iliould it be found
defective. The impoffibility 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 conjecture, hav-
ing recourfe to that elaflic fluid, the ex-
iftence of which in the volcano of Strom-
boli I believe certain, and which, in fome

meafure.

( 3^5 )

jneafure, 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 ad: 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. in. e c GHAPd

(386 )

CHAP. XXII.

DISCOVERY THAT VARIOUS VOLCANIC
PRODUCTS CONTAIN MURIATIC ACID
—ENQUIRY HOW THIS ACID HAS BEEN
PRODUCED, AND MIXED WITH THEM.

An acid liquor extradied from the /potted,
glafs of 'L'lpari^ during Ignition — Proofs
that this acid is muriatic — 'The fame r^-
fidt followed on a repetition of the experi'
me?it^-Afimilar acid liquor produced from
the black ghfs of Lipari--^Fa£fitious
glajfcs do notfiriiifj it — Proof both by the
dry and humid way^ that the muriatic acid
is not combined ivith thefe two glajjes^ but
only mechafiically united to their parts —
Seven other volpafiic produdis fubje&ed to
the fame experiments^ from fome of which
the fame acid liquor was obtained^ and
from others not—Difcovery that this acid
does not exiji in volcanic produSls when in

a fate

( 387 )

a fiatt of fufton or ignition^ but is intro"
duced afterwards — This muriatic acid not
derived from the muriate of ammo?iiac —
// is probable that it proceeds either from

fubterranean places^ or from the decompo-

Jition of the muriate of foda.

EAR the beginning of the former chap-
ter, it has been obferved that, when we
enquired whether volcanic products, placed
in matraffes and expofed to the fire, afforded
any gas, and of what nature, a method there
defcribed was adopted to afcertain whether
any liquor was produced from the fame.
It w^as alfo mentioned that fuch was ob-
tained, which was found to be of a very
lingular character, and of which a defcrip-
tion was referved for another place, as we
were then occupied in the details of the
gafificadons 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
accompanied it.

C c 2 I (hall

{ 388 )

I fliail begin by defcribing the manner
in which it was obtained from two fpecies
of the glafles of Lipari, the fpotted and the
black.

With refpeci to the former of thefe,
•when the fire began to heat confiderably
the matrafs, there appeared in the receiver 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 fmali
quantity of limpid liquor.

This ilqaor, on examination, manifefted
the following characters : Its weight was
1 44 grains ; and its tafte was that of di-
luted muriatic acid.

The ferruginous pruffiate of pot-afh, not
faturated, and the tind:ure of galls made
with fpirit of vdne, do not ihow any fign
cf iron.

The

( 3S9 )

The ammoniacal carbonate. In: like maa-
iier, exhibits no appearance of earth.

The tind;ure of turnfole becoming red,
ihows 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 Bergmann, compofmg the fourth part
C c 3 pf

( 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 ftony fubftance which had
not only been fufed, but even vitrified by
fubterranean fires. It could not be fufped:ed
that they had both adhered to the matrafs,
lince, 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 fa<^ de^
termined me to repeat the experiment with
the fame fpotted glafs. As I had feveral
large pieces of it, 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 difperfing, covered the fides with

a water

( 391 )

a water which, falling down, produced at
the bottom a tolerable quantity of liquor.
I 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
water mixed wdth the muriatic acid, it
being well known that this acid, when it
comes in contad 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 queflion, from its great affinity with
it, was abforbed by it.

But is this fa(ft confined to this particular
fpecies of volcanic produd:, or doe.^ 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. Th^ refult was not different.
From twelve ounces of this glafs I obtained
104 grains of 4 liquor which accumulated
at the bottom of the glafs receiver, by the
condenfation of the white vapours, and thq
liquor manifefled to the tafte the fame mu-
riatic acid, the prefence of which was con-
firmed by the fame proofs as before.

Notwithftanding the equality of the weight
of the two glaffes, the liquor obtained from
the prefent weighed 40 grains lefs than
that extracted from the other, but, when
touched with the point of the tongue, tailed
fomewhat more acid. In fad:, from 80
grains of this latter I obtained 10 grains of
muriate of filver, in which there was, con-
fequently, i^ grains of muriatic acid, while
the other only contained 2.

I afterwards made the fame experiment
on faditious glafs ; t>ut, in this cafe, not
more than a grain of water was collected in
the receiver, and that was perfedly infipid.
It appears, therefore, that this acid apper-
tains

( 393 )

|:ains to the two volcanic glafles, exclufiveiy

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 feme elucidation of this
doubt might be obtained by expofmg o.ae
of thefe two glaifes to a fire not fufficiently
ftrong to caufe fufion. I put fix ounces of
the fpottcd glafs, reduced to powder, in a
glafs retort with a luted belly ; joining to it
the glafs receiver, communicating as before
with 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 firil 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 matrafles, be-
caufe the heat was not fo great.

The

( 395 )

The humid way afforded a ftill 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 leaft change
the colour of the tind:ure of turnfole ; a
proof that in it there either exlfted no acid
difengaged, or that it was extremely weak.
On trying the fame water with 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
fl:reaks in the folution of the nitrate of fflver,
I entertained fome doubt whether this tur-
bidnefs might be the effect of this acid ;
and, to remove it, I refolved to try whether
a fimilar turbidnefs, but without fleeces or
flreaks, might not be produced by nitrate
of fflver in difl:illed water in which a drop
of muriatic acid had been infufed. On

making

{ 396 )

making this experiment I found that the
fleeces, on Increaiing the quantity of water^
became lefs fenfible in the infufion of folo-
tion of filver ; and, adding ftili more water,
a flight turbidnefs was at length produced
without fleeces or itreaks : v\?hence it ap-
peared evident that the turbidnefs in queftion
was the efFed; of a very flight portion of
the muriatic acid, which had palTed from
the volcanic glailes 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 fucceflfive times, fifteen
hours each time ; then ftraining off the watcFj
I evaporated it to drynefs, and found at the
bottom of the veffel a refidue of fine glafs-
powder. On. this I poured a little didilled
water, and tried one part of this water with
the tindiure of turnfole, and the other with
nitrate of filver. In the former arofe a thin
reddifh fume, and in the latter a flight tur^-
bidnefs, not without a few white fleeces.

I took

( Z9l )

1 took 19 ounces, 2 drams, and y^ grains
of black glafs of Lipari, broke it into fix
pieces, put them in diftilled water, and left
them during forty hours in a fand-bath,. but
without boiling. I did the fame by a
quantity of the fpotted glafs, broken into fe ven
pieces, and weighing 20 ounces, 2 drams,
and i^ grain. Having dried the two
glafles 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 fiiver, which caufed a flight tur-
bidnefs, and a proportionate fediment.

By all thefe fadis I think it is inconteft-
ably proved that the muriatic acid, in thefe
two volcanic glafTes, is not combined with
them fo as to enter into them as a conftitu-
ent principle ; but is only mechanically at-
tached to their parts.

Befides thefe tv/o glaifes, the black and
the fpotted of Lipari, I made experiments,
as I have mentioned in the preceding chap-
ter, on fix other volcanic products. The

gafeous

( 3P8 )

glfeous fubftances obtained from them fiave
been already defcribed. It now remains to
ftate the refuhs relative to the prefent en-
quiry.

From the lava of Vefuvlus, containing
garnets, was obtained in the receiver two
grains of water, which did not in the lead
change the tiadiure 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 deftitute
of muriatic acid.

The lava of Vefuvlus which had Howed a
fhort time before 1 vifited that volcano, left
at the bottom of the receiver four grains of
water, which, when tried by the re-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-
what acidulous ; and the precipitation in
white fleeces, caufed by the nitrate of fil-
ver.

( 399 )

f er, proved the prefence of the muriatic
acid.

The lava of Stromboli, thrown out of its
crater, furnifhed two grains of pure watev.

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 jl grains of water in which
was contained a portion of muriatic acid ; as
was difcoverable by touching it with the
tongue, and ftill more decifively by the fleecy
ilreaks produced by the nitrate of filver.

The lava which IfTued from Etna in the
year 1787, and which, like that of Strom-
boli, was ftill warm when I colledled it,
gave water to the amount of 6 grains, which
in every refpedl refembled diftilled water.

From a folid pumice of Lipari I obtained
24I: grains of water, which was acid to the
tafte, changed the tindure of turnfole to

red.

{ 4^0

fed, and the acid of which was manlfeftly'
muriatic, from the fleecy turbidnefs produced
by mixing it with the nitrate of filver.

On comparing all thefe fa£tSj it appears
that, of nine volcanic produd;s expofed to
the ad;ion of the fire and fufed, fix mani-
felled the prefence of the muriatic acid, and
in three not the leaR fign of it appeareda
From a comparifon of the local circum-
ftances of thefe nine products, we muft be
convinced that the muriatic acid does not
exifb in thef^ products when they are either
fufed, or heated to rednefs ; but that it
unites with them afterwards, fmce the three
lavas, one from Vefuvius, another from
Stromboli, and a third from Etna, which
had been recently ejected from the fubter-
ranean f-irnaces, contained none, though
they afforded a fmall portion of water ;
while the fix others which had ceafed to
burn for a longer or fliorter time, gave a
greater or lefs quantity of this acid. It is
alfo a confirmation of this fad:, and merits,
attention, that the fame lava of Stromboli
.5 was

( 40i )

Was deftitute of it when firft ejet^ted 5, .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 glafTes upon lime without
making ufe of the carbonate of pot-afh ;
but I did not perceive any thing of the'
ftrong 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 fubterraneati
places in which v^fc know that it is fome-
times found, or rather perhaps from the fea
penetrating beneath the volcanic mountains;
that it is generated from the decompofi-
tion of the muriate of foda, by the means of
fulphureous acids in which volcanos abound 5
and that, abforbed by the humidity of th?

VOL. III. E) d air.

( 4©2 )

air, it IS introduced witli if into the volcanic
products. 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
glafle^ of Lipari; and efpecially the black
fpecies, ks it is extremely compad, and has
not the leaii appearance of any cleft or
<;rack. But we know that water can fub-
tilize itfelf in fuch a maimer as to penetrate
other bodies equally folid and compa£l, in
' which our eyes, though alTifted by a lens of
a ftrong magnifying poWer, cannot difcover
the fjiiallefi: fiffure or minutefl: pore.

. ,; : 2KP OF THE THIRB VOI.UMI.

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