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ferent names, under the pretext that we have
found intermediate varieties which seem to con-
nect them, by appearing to belong equally to
the one and the other; without which, I repeat,
that we shall no longer distinguish genera nor



36 DOMAIN I. SIDEKOUS,

species; there would be but one and the same
name for all the mineral kingdom. Thus I dis-
tinguish granite from porphyry, porphyry from
trap, this from petrosilex, roches de corne, and
argillolites, because the well-characterised indi-
viduals of these different kinds are evidently
distinct; and I do not embarrass myself because
there are transitions or intermediate varieties,
which I do not exactly know to which kind I
ought to refer.

" I have in this only to regret a deviation
from the acceptation that M. Dolomieu has
given to the name of trap, in the excellent work
he published, Journal de Physique, An 2. Part I.
page 25?. He had given this name to the cor*
mus trapezius of Wallerius, which is a simple
stone of the genus corneennes, with a fine and
compact fracture. But I have already observed
in another place, that the genus of simple cor-
neennes does not require this subdivision, whilst
the class of composites or rocks appears inca-
pable of avoiding it; and of them the cele-
brated Werner has even formed such a class,
where, under the head of trapp formazion, he
includes grunstein, the amygdaldide t the por~
phyrsckiefer, and bazalt.

" I shall also observe, that the Swedes give
the name of trap, not only to a simple and com-



MODE III. BASALTIN. 37



pact corneenm, but also to composite rocks, or
to rocks of which this corneenne forms the ce-
ment; it is the saxum trapezium, Wall. Sp. 220.
We may also see the description that M. Nose
gives of 31 species of traps which he received
from Sweden, Beytrage, p. 401. seq. M. de
Faujas, in his little treatise upon traps, equally
gives to this word a very wide acceptation ; but
it does not seem conformable to the laws of a
good nomenclature, to give the same name to
substances which belong to different classes.

" It is according to these principles that
1 determined to confine the name of trap to
a composite rock, or to the rock of which
I have given a definition at the beginning of
this paragraph.

" 1946. The traps forming the cement of dif-
ferent variolites of the river Emme, vary in their
colours and nature. We see some of them grey,
others approaching to green, and others to a
violet colour; they are more or less hard, some
containing only in their glands free calcareous
parts ; others contain in their paste some which
become friable after having remained in the ni-
trous acid. Even the cement which unites the
grains or small crystals of these traps is for the
most part clay, hardened into argillolite, more
or less ferruginous. The little grains, I speak



38 DOMAIN I. SIDEROUS.

of those which compose the substance of traps,
and not of the large grains or glands which form
amygdaloids, these little grains, I say, are of
quartz, felspar, sometimes of hornblende, and of
that substance I have called granular chusite,
1944*."

Volcanoes. According to the present classification, ge-
nuine basalt, that of the ancients, must be omit-
ted in the dispute between the Neptunists and
Volcanists, which only regards basal tin. The
common trap of the Swedes and Germans is
always a basaltin ; and when stratified is allowed
even by Faujas not to be volcanic. The contest
therefore chiefly relates to the columnar basaltin,
which the French mineralogists infer to be always
of a volcanic origin ; while, as already observed,
it seems rather to arise from a phenomenon still
more grand and rare. The great chain of vol-
canoes in the Andes is chiefly argillaceous, or
clay porphyry ; and their most dangerous ejec-
tions are torrents of mud. In New Spain, where
the mountains are chiefly of clay- slate, a vol-

* Sauss. vii. 203. For the chusite of Saussure, see his Journey
to the extinct volcanoes of Brisgaw, Journ. de Ph. 17Q4, p. 325.

See also his account of pierres de come, 95 : most of them may
be scratched by the nail. He says, 103, that trap is A compact
pierre de corns 9 which not being a production of fire, is very different
from basalt. In 1525, Saussure doubts if the basaltin of the
extinct volcano of Beaulieu be volcanic.



MODE III. BASALTIC.

cano suddenly burst out in the vale of Jorullo,
1759; when, according to Humboldt, who saw
it in 1803, a basaltic cone appeared above
ground, of 1400 feet in height: but this cone
seems rather to have been developed than ele-
vated by the new volcano, as it could scarcely
be formed from fluid lava, which would be con-
tradictory to the common laws of hydrostatics.
The accounts of the volcanoes in the Andes are
far from being complete ; but there seems to be
little or no mention of basalt, and no hint of ba-
saltic columns ; which, if they were volcanic,
would be truly surprising in a chain which ex-
tends more than three thousand miles, and con-
tains about a hundred active volcanoes.

But as the presence of iron seems necessary
to volcanic inflammation, and the same metal
forms the ruling ingredient of basalt, it is no
wonder that this coincidence should have occa-
sioned a confusion of ideas. Around the grand
volcano of the isle of Bourbon, there are basaltic
rocks ; and where the basaltin contains sulphur,
it may be presumed to be a compact lava ; but
here are no ranges of those grand basaltic co-
lumns which distinguish Faroe, or StafFa. If we
return to Europe, the grand volcano of Etna has
probably been in a state of conflagration for
2500 years, and the circumference is computed



40



DOMAIN I. SIJDEROUS.



to extend to one hundred and thirty miles ; yet,
among the numerous hills which surround this
sublime volcano, there is none capped with ba-
saltic columns; and its lavas, after such nu-
merous ejections, do not seem even accidentally
to have assumed those elegant and precise forms*.
Dolomieu, and other prejudiced Volcanists, have
indeed observed instances of the lava divided into
rude prisms; but where is the representation
.of any Giants' Causey in Sicily ? Where the
base of Etna reaches the sea on the east the
shore is volcanic, or at leant supposed to be so,
for the space of twenty-three miles ; and for the
first seven or eight miles after leaving Catania,
Spallanzani indeed observed some prisms, more
or less characterised ; but the two other thirds of
this shore, though equally consisting of lava,
only present irregular fissures. It is presumed
that even the former bear but a slight resem-
blance to the beautiful articulated columns of
Staffa, or the Giants* Causey, especially as
figured by Da Costa and Pictet. It is also to be
questioned whether these columns of Etna be

* Von Troil has observed, that basaltic columns are common ip
Iceland ; but the people suppose their ranges the work of giants,
while, if they originated from the volcanoes, the circumstance
jvould strike the most common observer. They sometimes appear
among lava, sometimes among tufa; that is, they are preexistent
Jo either.



MODE 111. BASALTIN.



not composed of porous lava, as Dolomieu allows
that some are, while others, as he says, are com-
pact, because the water stops the internal effer-
vescence; and whether, if the observers had
seen the elegant articulated columns of the
north of Europe, they would not have rejected
the comparison*? But as Sicily may be said to
be in our possession, and the interesting work of
Dolomieu has not been translated into English,
it may not be irrelevant to present an extract,
that future o!> .orvers may decide whether the
appearances be caused by the eruptions, or be
antecedent to them.

<c As basaltic columns rarely appear in cabi- Basaitinof
nets, and it is more interesting to see them on
the spot, that their groups may be the better fol-
lowed, I shall point out those parts of Etna
where the most curious phenomena of this kind
may be observed.

" In the second of the Cyclopic isles, of
which the form is that of a long pyramid,
immense prismatic columns, perpendicular, ar-
ticulated, and for the most part hexagonal, ap-
pear -, the diameter of which is from two to three
feet.

* I have seen, in the beautiful collection of M. Patrin, at Paris,
berils articulated in the same manner with basaltin : but no one
has supposed that berils are produced by fire.



42 DOMAIN I. S1DEBOUS.

" In the two other Cyclopic isles there are
smaller columns, heaped upon each other, or
inclined in different directions.

" Upon the shore of la Trezza, near the pier,
there is a very curious group of little articulated
columns, which radiate from a common centre,
and form fasces singularly contorted ; the arti-
culations are marked, but the vertebra, so to
speak, do not separate.

" Upon the shore between the castle of laci
and la Trezza, there are many groups of ba-
saltic columns, piled in various ways.

" At the foot of the mountain of the castle of
laci, there are many groups of pyramidal diver-
gent columns.

" In the body of this mountain there are large
bowls, from two to four feet in diameter, like the
large balls of pyrites found in chalk, being
formed of pyramidal columns united by their
points in a common centre.

" In the mountains of la Trezza is found a
great number of prismatic columns, of different
forms and dimensions, many being displaced and
lying in the clay.

" At laci Reale, at the bottom of the cliffs on
the sea shore, are seen large prismatic columns,
subdivided into many smaller; while on the
shore there are many large prismatic columns



MODE III. BASALTIN, 43

rising from the sea, the tops forming a walk at
the bottom of the cliffs.

In the mountain of la Motta, two leagues
from Catania, there are veiy large and long
prismatic columns, in a vertical position, formed
of the most compact lava, which rings like
bronze.

" In the mountain of Paterno there are large
columns, ill figured.

" In the mountains of Licodia, near the spring
called Capo del Acqua, there is a wall of large
prismatic columns.

" Under the little town of Bianca Villa there
are cliffs formed by prismatic columns.

" In going from Bianca Villa to Aderno you
often walk on the tops of columns, which form
regular pavements, resembling the ancient Ro-
man ways. Within the town of Aderno there
are also several basaltic causeys.

" Between Aderno and Bronte, on taking the
lower road which follows the course of the river,
you walk for more than two leagues on a pave-
ment formed by the tops of columns ; and on
the right are the most beautiful walls of pris-
matic basalt which I have ever seen, the co-
lumns being mostly vertical. There may also be
observed in many places fasces of prisms, pro-
jecting from the wall, like epaulements or demi-



44 DOMAIN I. SIDEROUS.

bastions, The columns reunited by their sum-
mits, as i ito one head, enlarge according to their
length.

" Scattered prisms and walls of prismatic lavas
may also be found in many other places; form-
ing, as I have already mentioned, a kind of belt
around the skirts of Etna. Don Joseph Gioeni,
whom I have formerly celebrated, is occupied
with an elaborate description of the prismatic
lavas of the volcano : and he will add prints
which can alone express the variety of their
forms, and the manner in which they are
grouped*."

If these representations be exact, they would
certainly induce us to believe that prismatic
basaltin is the product of volcanic fires ; and an
admirer of nature would willingly embrace a
new and important discovery, which would afford
greater variety to his views, and more striking
topics for his contemplation. With regard to
the British dominions, in particular, a volcano,
even extinct, might be regarded as a grand and
curious acquisition. The great number of vol-

* Dolomieu, Etna, p. 455 . It must not however be forgotten
that, p. 192, he allows that all these columns present small pores,
visible by a lens; nay, p. 180, he regards all lavas as compact which
contain spaces of some inches without pores. But he might say,
as compactness is owing to refrigeration, that, in the cold and moist
regions of the north, lavas are more compact.



MODE III. BASALTIN.



canoes which exist, or have existed, in Iceland,
the southern skirts of which can alone be said to
be known to naturalists, might well authorise us
to believe that a chain of volcanoes may have
existed in a tract of country, or isles, between
the north of Ireland and Faroe, and which have
been submerged, the foundations being destroyed
by the violence of their own conflagrations, and
the fury of the Atlantic /ocean. There are
indeed, according to Landl, evidences of a vi-
treous lava in one of the isles of Faroe; and my
intelligent friend Mr. Browne, who has pene-
trated so far into Africa, and has pervaded many
parts of Asia and Europe, was convinced that
he observed a wall of porous lava near Belfast;
but still there is no appearance of any craters.
Perhaps a disciple of Dolomieu, certainly a great
and respected name, " clarum et vemrabile no-
men" would be contented with one enormous
volcano between the north of Ireland and StafTa,
and another among the Faroe isles ; for the ex-
terior chain of the Hebudes is granitic, as are
most of the Shetland islands ; while the Orki> ?ys
consist of argillaceous sand-stone ; and non of
them can, on any theory, be said to present vol-
canic appearances.

However this be, as the genuine basalt, that of



46 DOMAIN I. SIDEROUS.

the ancients, is allowed on all hands not to be
of a volcanic nature, the distinct name basaltin
becomes the more necessary, in order to discri-
minate a wholly different substance, the origin
of which is still liable to contestation.

Concerning basaltin, by many called compact
lava, further observations will be fo- nd in dis-
cussing the Volcanic Rocks. The testimony of
Daubuisson, concerning the volcanic origin of
this substance, is too remarkable to be omitted,
as in his able treatise on basalt he has strongly
enforced the contrary opinion, embraced while
he was at Freyberg, and enveloped in the vortex
of Werner. This change of his Neptunean ideas
occurred after his visit to Auvergne, a country
which presents many extinct volcanoes, as all
who have seen it or its products must confess ;
this curious fact being only denied by those who
are lost in the mist of prejudice, and who in fact
ruin their own system, by pushing it so far as to
maintain tenets palpably absurd, and contradic-
tory to the common sense of mankind; such as,
for example, that pumice itself is of an aqueous
origin ! The following abstract of Daubuisson's
remarks on Auvergne is given in the Journal dc
Physique*.

* 1804.



MODE III. BASALTIN-. , 47

" After having given a preliminary idea of
the topographical position of Auvergne, and the
mineralogical structure of this country, M.
Daubuisson has successively and in detail de-
scribed the volcanoes and basalts of the country
of Puy de Dome, Mont Dor*, and of Cantal, he
concludes his memoir by a general review of his
observations. We shall here give an extract
from this latter part.

" Auvergne (Departments of the Puy de Dome
and of Cantal) is in the middle of that great
slope, or inclined plane, whose bottom lies to-
wards the center of France, and which terminates
in the upland that directs the course of the
Rhone to the westward. The primitive soil (an-
terior to the volcanoes) is of granite, covered
in some places with a marly limestone. The
valleys excavated in this soil render the country
unequal, and give it a mountainous appearance,
although there are in fact only excrescences or
volcanic mountains, which rise above the general
plane of the slope.

" Nearly all this soil has been covered with
volcanic productions : they are of three kinds,
and their formation seems to date from three
distinct epochs. The most recent and least

* This is the proper spelling, derived from the river Dor, which,
joining the Dogne, forms the Dordogne. See Le Grand.



43 BOMAIN I. SIDEROU9.

numerous are currents of lava, which lead to
craters still existing ; the second are masses or
tables of basalt, separated by rifts or valleys 5
the third consists of mountains whose mass is a
kind of volcanic porphyry.

" 1st. Lava in form of currents. There are in?
Auvergne near a hundred conical, isolated moun-.
tains, from 200 to 400 yards in height, formed
of heaps of scoriae, fragments of lava and of la-
pillo : their summit often presents a hollow in
the form of a cup or crater : they rest imme-
diately on granite. From the bottom of several
of them currents are observed to run of lava of a
basaltic nature, that is of a greyish black, with
a fine compact grain: this lava contains grains
and crystals of peridot (olivine), augite, felspar,
&c. The superficies is blistered and studded
with asperities, which sometimes attain- and even
surpass a yard in height: the interior is more
compact, and less porous, as you arrive nearer
to the bottom. The currents are spread in the
adjacent plain ; they have sometimes reached
the bottom of certain valleys, and have followed
their course for a distance of three or four
leagues ; in advancing progressively they always
incline to points lower and lower; they follow
the inequalities of the soil ; they separate on
meeting with any obstructing eminences in their



MODE III. BASALTIN. 49

passage. In fact, like the courses of fluid mat-
ter> they have been subservient to all the laws of
hydrodynamics. The history of these currents
of lava is complete, and there is nothing left to
the imagination to supply. We behold the ori-
fice from whence they issued, the course they
pursued, the country they occupy, &c.

" They flowed upon granite : their substance
then was either in or under that rock ; now these
lavas contain from 15 to 20 per cent, of iron ;
the granite possesses scarcely any ; they do not
therefore consist of granite, fused and wrought
by volcanic agents : we must therefore, with
Dolomieu, seek under this rock, for the matter
which has yielded this substance ; but here we
can only form conjectures. The cause which
may have developed this subterranean fire, the
combustible matter which may have maintained
it, are entirely unknown to us. It is not coal, or
bituminous matter, for they are only found in
secondary regions, and never either in or under
granite : it does not consist in pyrites^ because
pyrites, alone and enclosed in the bosom of the
earth, never decompose, and generate no heat.
As for the period when these lavas flowed, al-
though anterior to the history or tradition of
mankind, it is nevertheless very recent when
compared with those vast degradations which

VOL. i.



.50 DOMAIN I. SIDEROUS.

the surface of the globe presents : it is posterior
to the entire excavation of the valleys, since it
occupies their bottoms.

" 2d. Basalts. The volcanic productions of
the second kind, are basalts, which, under the
form of sheets, tables, peaks, cover the elevated
parts of the ancient soil, or constitute the sum-
mit of some mountains and isolated eminences ;
they are also observed on almost all the skirts of
Mont Dor and Cantal ; they are evidently only
jthe remains and patches of different currents y
which have spread over the country j they pre-
sent the same mineralogical characters as the
basalts of other countries, Saxony, &c. ; they
contain the same substances ; they equally in-
cline to a prismatic division ; they cover without
distinction all kinds of rocks, and are never
covered by them, &c.

" A volcanic origin cannot be denied to these
basalts. The perfect resemblance between their
paste and that of some parts of currents of lava
which are found in the neighbourhood, and
which have come from a crater still existing, is
already a very strong presumption; but they
present other infallible marks of this origin.
1. In following step by step certain masses of
basalt which are near Mont Dor and Cantal,
and supplying by the imagination what has vi-




MODE III. BASALtlN.



sibly been taken away, you arrive at the sides
of those two enormous volcanic mountains, and
you come to masses of scoriae or of blistered
rocks, where, beyond doubt, we are near the
source of the current ; all the basalts which have
been followed upwards, made part of that cur-
rent. 2. A great number of those large basaltic
platforms which cover isolated mountains, dis-
play on their surface blisters, spongy scoriae, or
drosses, like those which are observed on the
best preserved lavas ; nor can we refuse them a
similar origin. Some others of these platforms
repose on volcanic ashes. 3. Some isolated
eminences present, it is true, summits of black
basalt, compact, prismatic, destitute of those un-
equivocal signs of the action of fire which are seen
elsewhere ; but the greatest part of them stands
by the side of those platforms with scoriated sur-
faces of which we have just spoken : they once
formed with them a continued whole, and have
evidently only been divided from them by the
excavation of the valleys and ravines which now
separate them. They cannot have had a differ-
ent origin ; the corrosive action of time and the
elements must have destroyed the scorified bark;
only the compact nucleus would remain, de-
prived of the marks of the action of fire, as are
the interior parts of the greater portion of lavas

E 2



DOMAIN I. SIDEROUS.

in currents. Thus all the basalts of Auvergne
^present proofs, either direct or indirect, of a vol-
canic origin; though the degradation of the
soil, the dismemberment that the currents have
suffered, no longer permit us to retrace the cra-
ter from whence they flowed, nor to see the
number, form, or extent, of the different cur-
rents : the only positive thing we can say in
regard to them is, that their existence is anterior
to the excavation of the valleys.

" 3. Porphyroid Masses. The third species
of volcanic productions of Auvergne is quite of
a peculiar nature ; they are grey stony masses,
of a porphyritic structure; they form eight or
ten distinct mountains : the most considerable
are Cantal, whose diameter at the base may be
about nine or ten leagues, and 900 or 1000 yards
high, above its bottom ; the Mont Dor, whose
base is five or six leagues, and its height from
1000 to 1100 yards; the Puy de Dome, whose
base is half a league in diameter, and 600 yards
high : the other mountains are still less. The
two first are vast masses, torn and irregularly
cut by the action of the waters. The substance
of which they are all composed is grey, often
approaching to black, sometimes to green ; its
fracture dull and earthy, with coarser or finer
grains ; it has little hardness, and easily decom-



MODE III. BASALTIN.



poses j its weight is about twice and a half
greater than that of water ; it melts easily under
the blowpipe into white amel*, and seems to be
composed of the same elements as felspar, but
confusedly united ; it contains a great quantity
of crystals of felspar, some acicular crystals of
hornblende, and even some spangles of mica.
The klingstein-porphyr of the Germans f, which
is found in considerable quantity at Mont Dor
and Cantal, seems to be only a remarkable va-
riety.

" These porphyroid masses so nearly resemble
certain productions in the humid way, that it
required nothing less than their extraordinary
position, their situation in the midst of volcanoes,
some unequivocal marks of the action of fire,
their passage direct or indirect to basalt, and
above all the volcanic scoriae imbedded in their
mass, to prove that they are foreign and poste-
rior to the productions in the humid way, and
that they owe their existence to the volcanoes.

" Nothing positive can be said as to the man-
ner in which they have been produced, and
arrived at their present position. No where is

* See Johnson. Enamel is properly the application of the amel
to another substance.

f Klaproth procured 8 per cent, of soda from cnat of Bohemia,
and Mr. Bergman 6 from that of Mont Dor.



DOMAIN I. SIDEROUS.




there observed any crater from which they could
have issued, nor distinct currents by which they
might be traced to their origin. It might be
thought that they consist of melted granite,
wrought and ejected by volcanic agents. The
homogenity of their paste shows how complete
the fusion or igneous dissolution has been, and
scarcely permits one to believe that the number
of crystals of felspar which they contain, should



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