Cosmos: A Sketch of the Physical Description of the Universe Part 22

[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 ill.u.s.trate 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 quant.i.ty 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 a.n.a.lyses 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 h.e.l.lenic 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 Ca.s.sotis (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] *Ca.s.sotis (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 ma.n.u.script 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 pa.s.sage 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 quant.i.ty 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 pa.s.sage 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 ma.s.ses of rock were torn up and scattered around. Similar ma.s.ses may be seen round the now inactive mud volcano of Monte Ziblo, near Sa.s.suolo, 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 cont.i.tiguous 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 ma.s.ses 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 const.i.tutes 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 acc.u.mulating in the interior before it could overpower the resistance of the ma.s.s pressing upon it; it sometimes, for instance, on the origin of new islands, will raise granular rocks and conglomerated ma.s.ses (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 ma.s.s 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. x.x.xvii., 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. (La.s.sen '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 s.h.i.+ning mountain, if Voss is correct in stating that [Greek work] is an h.e.l.lenic sound, and is connected with [Greed word] and [Greek word]; but the intelligent writer Parthey doubts this h.e.l.lenic origin on etymological grounds, and also because etna was by no means regarded as a luminous beacon for s.h.i.+ps 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.