p 221
when they are unmixed with the waters rising from great depths, or
descending from considerable mountain elevations, and when they have passed
through a long course at a depth from the surface of the earth which is
equal in our latitudes to 40 or 60 feet, and according to Boussingault, to
about one foot in the equinoctial regions,* these being the depths at which
the invariability of the temperature begins in the temperate and torrid
zones, that is to say, the depths at which horary, diurnal, and monthly
changes of heat in the atmosphere cease to be perceived.
[footnote] * The profound investigations of Boussingault fully convince me,
that in the tropics, the temperature of the ground, at a very slight depth,
exactly corresponds with the mean temperature of the air. The following
instances are sufficient to illustrate this fact:
________________________________________________________
Stations Temperature at Mean Height, in
within 1 French foot Temperature English
Tropic [1.006 of the of the feet, above
Zones. English foot] air. the level
below the of the sea.
earth's surface.
________________________________________________________
Guayaquil 78.8 78.1 0
Anserma Nuevo 74.6 74.8 3444
Zupia 70.7 70.7 4018
Popayan 64.7 65.6 5929
Quito 59.9 59.9 9559
________________________________________________________
The doubts about the temperature of the earth within the tropics, of which I
am probably, in some degree, the cause, by my observations on the Cave of
Caripe (Cueva del Guacharo), 'Rel. Hist.', t. iii., p. 191-196), are
resolved by the consideration that I compared the presumed mean temperature
of the air of the convent of Caripe, 65.3 degrees, not with the temperature
of the air of the cave, 65.6 degrees, but with the temperature of the
subterranean stream, 62.3degrees, although I observed ('Rel. Hist.', t.
iii., p. 146 and 195) that mountain water from a great height might probably
be mixed with the water of the cave.
Hot springs issue from the most various kinds of rocks. The hottest
permanent springs that have hitherto been observed are, as my own researches
confirm, at a distance from all volcanoes. I will here advert to a notice
in my journal of the Aguas Calientes de las Trincheras', in South America,
between Porto Cabello and Nueva Valencia, and the 'Aguas de Comangillas', in
the Mexican territory, near Guanaxuato; the former of these, which issued
from granite, had a temperature of 194.5 degrees; the latter, issuing from
basalt, 205.5degrees. The depth of the source from whence the water flowed
with this temperature, judging from what we know of the law of the increase
of heat in the interior of the earth, was probably 7140 feet, or above two
miles. If the universally-diffused terrestrial heat be the cause of thermal
springs, as of active volcanoes, the rocks can only exert an influence by
the different capacities
p 222
for heat and by their conducting powers. The hottest of all permanent
springs (between 203 degrees and 209 degrees) are likewise, in a most
remarkable degree, the purest, and such as hold in solution the smallest
quantity of mineral substances. Their temperature appears, on the whole, to
be less constant than that of springs between 122 degrees and 165 degrees,
which in Europe, at least, have maintained, in a most remarkable manner,
their 'invariability of heat and mineral contents' during the last fifty or
sixty years, a period in which thermometrical measurements and chemical
analyses have been applied with increasing exactness. Boussingault found in
1823 that the thermal springs of Las Tricheras had risen 12 degrees during
the twenty-three years that had intervened since my travels in 1800.*
[footnote] *Boussingault, in the 'Annales de chimie', t. lii., p. 181. The
spring of Chaudes Aigues, in Auvergne, is only 176degrees. It is also to be
observed, that while the Aguas Calientes de las Trincheras, south of Porto
Cabello (Venezuela), springing from granite cleft in regular beds, and far
from all volcanoes, have a temperature of fully 206.6 degrees, all the
springs which rise in the vicinity of still active volcanoes (Pasto,
Cotopaxi, and Tunguragua) have a temperature of only 97 - 130 degrees.
This calmly-flowing spring is therefore now nearly 12 degrees hotter than
the intermittent fountains of the Geyser and the Strokr, whose temperature
has recently been most carefully determined by Krug of Nidda. A very
striking proof of the origin of hot springs by the sinking of cold meteoric
water into the earth, and by its contact with a volcanic focus, is afforded
by the volcano of Jorulla in Mexico, which was unknown before my American
journey. When, in September, 1759, Jorullo was suddenly elevated into a
mountain 1183 feet above the level of the surrounding plain, two small
rivers, the 'Rio de Cuitimba' and 'Rio de San Pedro', disappeared, and some
time afterward burst forth again, during violent shocks of an earthquake, as
hot springs, whose temperature I found in 1803 to be 186.4 degrees.
The springs in Greece still evidently flow at the same places as in the
times of Hellenic antiquity. The spring of Erasinos, two hours' journey to
the south of Argos, on the declivity of Chaon, is mentioned by Herodotus.
At Delphi we still see Cassotis (now the springs of St. Nicholas) rising
south of the Lesche, and flowing beneath the Temple of Apollo; Castalia, at
the foot of Phaedriadae; Pirene, near Acro-Corinth; and the hot baths of
Aedipsus, in Euboea, in which Sulla bathed during the Mithridatic war.*
[footnote] *Cassotis (the spring of St. Nicholas) and Castalia, at the
Phaedriadae, mentioned in Pausanias, x., 24, 25, and x., 8, 9; Pirene
(Acro-Corinth), in Strabo, p. 379; the spring of Erasinos, at Mount Chaon,
south of Argos, in Herod., vi., 67, and Pausanias, ii., 24, 7; the springs
of Aedipsus in Euboea, some of which have a temperature of 88 degrees, while
in others it ranges between 144) qne 167 degrees, in Strabo, p. 60 and 447,
and Athenaeus, ii., 3, 73; the hot springs of Thermopylae, at the foot of
Oeta, with a temperature of 149 degrees. All from manuscript notes by
Professor Curtius, the learned companion of Otfried Muller.
I advert with pleasure to these
p 223
facts, as they show us that, even in a country subject to frequent and
violent shocks of earthquakes, the interior of our planet has retained for
upward of 2000 years its ancient configuration in reference to the course of
the open fissures that yield a passage to these waters. The 'Fontaine
jaillissante' of Lillers, in the Department des Pas de Calais, which was
bored as early as the year 1126, still rises to the same height and yields
the same quantity of water; and, as another instance, I may mention that the
admirable geographer of the Caramanian coast, Captain Beaufort, saw in the
district of Phaselis the same flame fed by emissions of inflammable gas
which was described by Pliny as the flame of the Lycian Chimera.*
[footnnote] (Pliny, ii., 106; Seneca, 'Epist.' 79, 3, ed. Ruhkopf
(Beaufort, 'Survey of the Coast of Karamania', 1820, art. Yanar, near
Delktasch, the ancient Phaselis, p. 24). See also Ctesias, 'Fragm.', cap.
10 p. 250, ed. Bahr; Strabo, lib. xiv., p. 666, Casaub.
["Not far from the Deliktash, on the side of a mountain, is the perpetual
fire described by Captain Beaufort. The travelers found it as brilliant as
ever, and even somewhat increased; for, besides the large flame in the
corner of the ruins described by Beaufort, there were small jets issuing
from crevices in the side of the crater-like cavity five or six feet deep.
At the bottom was a shallow pool of sulphureous and turbid water, regarded
by the Turks as a sovereign remedy for all skin complaints. The soot
deposited from the flames was regarded as efficacious for sore eyelids, and
valued as a dye for the eyebrows." See the highly interesting and accurate
work, 'Travels in Lycia', by Lieut. Spratt and Professor E. Forbes.] -- Tr.
The observation made by Arago in 1821, that the deepest Artesian wells are
the warmest,* threw great light on the origin of thermal springs, and on the
establishment of the law that terrestrial heat increases with increasing
depth.
[footnote] *Arago, in the 'Annuaire pour' 1835, p. 234.
It is a remarkable fact, which has but recently been noticed, that at the
close of the third century, St. Patricus,* probably Bishop of Pertusa, was
led to adopt very correct views regarding the phenomenon of the hot springs
at Carthage.
[footnote] *'Acta S. Patricii', p. 555, ed. Ruinart, t. ii., p. 385,
Mazochi. Dureau de la Malle was the first to draw attention to this
remarkable passage in the 'Recherches sur la Topographie de Carthage', 1835,
p. 276. (See, also, Seneca, 'Nat. Quaest.', iii., 24.)
On being asked what was the cause of boiling water bursting from the earth,
he replied, "Fire is nourished in the clouds and in the interior
p 224
of the earth, as Aetna and other mountains near Naples may teach you. The
subterranean waters rise as if through siphons. The cause of hot springs is
this: waters which are more remote from the subterranean fire are colder,
while those which rise nearer the fire are heated by it, and bring with them
to the surface which we inhabit an insupportable degree of heat."
As earthquakes are often accompanied by eruptions of water and vapors, we
recognize in the 'Salses',* of small mud volcanoes, a transition from the
changing phenomena presented by these eruptions of vapor and thermal springs
to the more powerful and awful activity of the streams of lava that flow
from volcanic mountains.
[footnote] *[True volcanoes, as we have seen, generate sulphureted hydrogen
and muriatic acid, upheave tracts of land, and omit streams of melted
feldspathic materials; salses, on the contrary, disengage little else but
carbureted hydrogen, together with bitumen and other products of the
distillation of coal, and pour forth no other torrents except of mud, or
argillaceous materials mixed up with water. Daubeney, op cit., p. 540.] --
Tr.
If we consider these mountains as springs of molten earths producing
volcanic rocks, we must remember that thermal water, when impregnated with
carbonic acid and sulphurous gases, are continually forming horizontally
ranged strata of limestone (travertine) or conical elevations, as in
Northern Africa (in Alberia), and in the Banos of Caxamarca, on the western
declivity of the Peruvian Cordilleras. The travertine of Van Diemen's Land
(near Hobart Town) contains, according to Charles Darwin, remains of a
vegetation that no longer exists. Lava and travertine, which are constantly
forming before our eyes, present us with the two extremes of geognostic
relations.
'Salses' deserve more attention than they have hitherto received from
geognosists. Their grandeur has been overlooked because of the two
conditions to which they are subject; it is only the more peaceful state, in
which they may continue for centuries, which has generally been described:
their origin is, however, accompanied by earthquakes, subterranean thunder,
the elevation of a whole district, and lofty emissions of flame of short
duration. When the mud volcano of Jokmali began to form on the 27th of
November, 1827, in the peninsula of Abscheron, on the Caspian Sea, east of
Baku, the flames flashed up to an extraordinary height for three hours,
while during the next twenty hours they scarcely rose three feet above the
crater, from which mud was ejected. Near the village of Baklichli, west of
Baku, the flames rose so high that
p 225
they could be seen at a distance of twenty-four miles. Enormous masses of
rock were torn up and scattered around. Similar masses may be seen round
the now inactive mud volcano of Monte Ziblo, near Sassuolo, in Northern
Italy. The secondary condition of repose has been maintained for upward of
fifteen centuries in the mud volcanoes of Girgenti, the 'Macalubi', in
Sicily, which have been described by the ancients. These salses consist of
many contitiguous conical hills, from eight to ten, or even thirty feet in
height, subject to variations of elevation as well as of form. Streams of
argillaceous mud, attended by a periodic development of gas, flow from the
small basins at the summits, which are filled with water; the mud, although
usualy cold is sometimes at a high temperature, as at Damak, in the province
of Samarang, in the island of Java. The gases that are developed with loud
noise differ in their nature consisting for instance, of hydrogen mixed with
naphtha, or of carbonic acid, or, as Parrot and myself have shown (in the
peninsula of Taman, and in the 'Volcancitos de Turbaco', in South America),
of almost pure nitrogen.*
[footnote] *Humboldt, 'Rel. Hist.', t. iii., p. 562-567; 'Asie Centrale',
t. i., p. 43; t. ii., p. 505-515; 'Vues des Cordilleres', pl. xli.
Regarding the 'Macalubi', the 'overthrown' or 'inverted', from the word
'Khalaba'), and on "the Earth ejecting fluid earth," see Solinus, cap. 5:
"idem ager Agrigentinus eructat limosas scaturigenes, et ut venae fontium
sufficiunt rivis subjinistrandis, ita in hac Sicilae parte solo munquam
deficiente, Aeterna rejectatione terram terra evomit."
Mud volcanoes, after the first violent explosion of fire, which is not,
perhaps, in an equal degree common to all, present to the spectator an image
of the uninterrupted but weak activity of the interior of our planet. The
communication with the deep strata in which a high temperature prevails is
soon closed, and the coldness of the mud emissions of the salses seems to
indicate that the seat of the phenomenon can not be far removed from the
surface during their ordinary condition. The reaction of the interior of
the earth on its external surface is exhibited with totally different force
in true volcanoes or igneous mountains, at points of the earth in which a
permanent, or, at least, continually-renewed connection with the volcanic
force is manifested. We must here carefully distinguish between the more or
less intensely developed volcanic phenomena, as for instance, between
earthquakes, thermal, aqueous, and gaseous springs, mud volcanoes, and the
appearance of bell-formed or dome-shaped trachytic rocks without openings;
the opening of these rocks, or of the elevated beds of basalt, as
p 226
craters of elevation; and, lastly, the elevation of a permanent volcano in
the crater of elevation, or among the 'debris' of its earlier formation. At
different periods, and in different degrees of activity and force, the
permanent volcanoes emit steam acids, luminous scoriae, or, when the
resistance can be overcome, narrow, band-like streams of molten earths.
Elastic vapors sometimes elevate either separate portions of the earth's
crust into dome-shaped unopened masses of feldspathic trachyte and dolerite
(as in Puy de Dome and Chimborazo), in consequence of some great or local
manifestation of force in the interior of our planet, or the upheaved strata
are broken through and curved in such a manner as to form a steep rocky
ledge on the opposite inner side, which then constitutes the inclosure of a
crater of elevation. If this rocky ledge has been uplifted from the bottom
of the sea, which is by no means always the case, it determines the whole
physiognomy and form of the island. In this manner has arisen the circular
form of Palma, which has been described with such admirable accuracy by
Leopold von Buch, and that of Nisyros,* in the Aegean sea.
[footnote] *See the interesting little map of the island of Nisyros, in
Roise's 'Reisen auf den Griechischen Inseln', bd. ii., 1843, s. 69.
Sometimes half of the annular ledge has been destroyed, and in the bay
formed by the encroachment of the sea corallines have built their cellular
habitations. Even on continents craters of elevation are often filled with
water, and embellish in a peculiar manner the character of the landscape.
Their origin is not connected with any determined species of rock: they
break out in basalt, trachyte, leucitic porphyry (somma), or in doleritic
mixtures of augite and labradorite; and hence arise the different nature and
external conformation of these inclosures of craters. No phenomena of
eruption are manifested in such craters, as they open no permanent channel
of communication with the interior, and it is but seldom that we meet with
traces of volcanic activity either in the neighborhood or in the interior of
these craters. The force which was able to produce so important an action
must have been long accumulating in the interior before it could overpower
the resistance of the mass pressing upon it; it sometimes, for instance, on
the origin of new islands, will raise granular rocks and conglomerated
masses (strata of tufa filled with marine plants) above the surface of the
sea. The compressed vapors escape through the crater of elevation, but a
large mass soon falls back and closes the opening, which had been only
formed by these manifestations of force. No volcano can, therefore,
p
be produced.*
[footnote] *Leopold von Buch, 'Phys. Beschreibung der Canarischen Inseln',
s. 326; and his Memoir 'uber Erhebungscratere und Vulcane', in Poggend.,
'Annal.', bd. xxxvii., s. 169.
In his remarks on the separation of Sicily from Calabria, Strbo gives an
excellend description of the two modes in which islands are formed: "Some
islands," he observes (lib. vi., p. 258, ed. Casaub.), "are fragments of the
continent, others have arisen from the sea, as even at the present time is
known to happen; for the islands of the great ocean, lying far from the main
land, have probably been raised from its depths, while, on the other hand,
those near promontories appear (according to reason) to have been separated
from the continent."
A volcano, properly so called, exists only where a permanent connection is
established between the interior of the earth and the atmosphere, and the
reaction of the interior on the surface then continues during long periods
of time. It may be interrupted for centuries, as in the case of Vesuvius
Fisove,* and then manifest itself with renewed activity.
[footnote] *Ocre Fisove (Mons Vesuvius) in the Umbrian language. (Lassen
'Deutung der Eugubinischen Tafeln in Rhein. Museum', 1832, s. 387.) The
word 'ochre' is very probaby genuine Umbrian, and means, according to
Festus, 'mountain'. Aetna would be a burning and shining mountain, if Voss
is correct in stating that [Greek work] is an Hellenic sound, and is
connected with [Greed word] and [Greek word]; but the intelligent writer
Parthey doubts this Hellenic origin on etymological grounds, and also
because etna was by no means regarded as a luminous beacon for ships or
wanderers, in the same manner as the ever-travailing Stromboli (Strongyle),
to which Homer seems to refer in the Odyssey (xii., 68, 202, and 219), and
its geographical position was not so well determined. I suspect that tna
would be found to be a Sicilian word, if we had any fragmentary materials to
refer to. According to Diodorus (v., 6), the Sicani, or aborigines
preceding the Sicilians, were compelled to fly to the western part of the
island, in the consequence of successive eruptions extending over many
years. The most ancient eruption of Mount Aetna on record is that mentioned
by Pindar and Schylus, as occurring under Hiero, in the second year of the
75th Olympiad. It is probable that Hesiod was aware of the devastating
eruptions of Aetna before the period of Greek immigration. There is,
however, some doubt regarding the work [Greek word] in the text of Hesiod, a
subject into whci I have entered at some length in another place.
(Humboldt, 'Examen Crit. de le Geogr.', t. i., p. 168.)
In the time of Nero, men were disposed to rank Aetna among the volcanic
mountains which were graduallybecoming extinct,* and subsequently Aelian**
even maintained that mariners could no longer see the sinking summit of the
mountain from so great a distance at sea.
[footnote] *Seaeca. 'Epist.', 79.
[footnote] ** Aelian, 'Var. Hist.', viii., 11.
Where these evidences -- these old scaffoldings of eruption, I might almost
say -- still exist, the volcano rises from a crater of elevation, while a
high rocky wall surrounds, like an amphitheater, the isolated conical mount,
and forms around it a kind of easing of highly elevated
p 228
strata. Occasionally not a trace of this inclosure is visible, and the
volcano, which is not always conical rises immediately from the neighboring
plateau in an elongated form, as in the case of Pichincha,* at the foot of
which lies the city of Quito.
[footnote] *[This mountain contains two funnel-shaped craters, apparently
resulting from two set of eruptions: the western nearly circular, and
having in its center a cone of eruption, from the summit and sides of which
are no less than seventy vents, some in activity and others extinct. It is
probable that the larger number of the vents were produced at periods
anterior to history. Caubney, op. cit., p. 488.] -- Tr.
As the nature of rocks, or the mixture (grouping) of simple minerals into
granite, gneiss, and mica slate, or into trachyte, basalt, and dolorite, is
independent of existing climates, and is the same under the most varied
latitudes of the earth, so also we find every where in inorganic nature that
the same laws of configuration regulate the reciprocal superposition of the
strata of the earth's crust, cause them to penetrate one another in the form
of veins, and elevate them by the agency of elastic forces. This constant
recurrence of the same phenomena is most strikingly manifested in volcanoes.
When the mariner, amid the islands of some distant archipelago, is no
longer guided by the light of the same stars with which he had been familiar
in his native latitude, and sees himself surrounded by palms and other forms
of an exotic vegetation, he still can trace, reflected in the individual
characteristics of the landscape, the forms of Vesuvius, of the come-shaped
summits of Auvergne, the craters of elevation in the Canaries and Azores, or
the fissures of eruption in Iceland. A glance at the satellite of our
planet will impart a wider generalization to this analogy of configuration.
by means of the charts that have been drawn in accordance with the
observations made with large telescopes, we may recognize in the moon, where
water and air are both absent, vast craters of elevation surrounding or
supporting conical mountains, thus affording incontrovertible evidence of
the effects produced by the reaction of the interior on the surface, favored
by the influence of a feebler force of gravitation.