cavities may perhaps favor the direction of undulations parallel to them;
occasionally, however, the waves of commotion intersect several chains
almost perpenducularly. Thus we see them simultaneously breaking through
the littoral chain of Venezuela and the Sierra Parime. In Asia, shocks of
earthquakes have been propagated from Lahore and from the foot of the
Himalaya (22d of January, 1832) transversely across the chain of the Hindoo
Chou to Badakschan, the upper Oxus, and even to Bokhara.*
[footnote] *Sir Alex. Burnes, 'Travels in Bokhara', vol. i., p. 18; and
Wathen, 'Mem. on the Usbek State', in the 'Journal of the Asiatic Society of
Bengal', vol. iii., p. 337.
The circles of commotion unfortunately expand occasionally in consequence of
a single and usually violent earthquake. It is only since the destruction
of Cumana, on the 14th of December, 1797, that shocks on the southern coast
have been felt in the mica slate rocks of the peninsula of Maniquarez,
situated opposite to the chalk hills of the main land. The advance
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from south to north was very striking in the almost uninterrupted
undulations of the soil in the alluvial valleys of the Mississippi, the
Arkansas, and the Ohio, from 1811 to 1813. It seemed here as if
subterranean obstacles were gradually overcome, and that the way being once
opened, the undulatory movement could be freely propagated.
Although earthquakes appear at first sight to be simply dynamic phenomena of
motion, we yet discover, from well-attested facts, that they are not only
able to elevate a whole district above its ancient level (as for instance,
the Ulla Bund, Delta of the Indus, or the coast of Chili, in November,
1822), but we also find that various substances have been ejected during the
earthquake, as hot water at Catania in 1818; hot steam at New Madrid, in the
Valley of the Mississippi, in 1812; irrespirable gases, 'Mofettes', which
injured the flocks grazing in the chain of the Andes; mud, black smoke, and
even flames, at Messina in 1781, and at Cumana on the 14th of November,
1797. During the great earthquake of Lisbon, on the 1st of November, 1755,
flames and columns of smoke were seen to rise from a newly-formed fissure in
the rock of Alvidras, near the city. The smoke in this case became more
dense as the subterranean noise increased in intensity.*
[footnote] * 'Philos. Transaci.', vol. xlix. p. 414.
At the destruction of Riobamba, in the year 1797, when the shocks were not
attended by any outbreak of the neighboring volcano, a singular mass called
the 'Moya' was uplifted from the earth in numerous continuous conical
elevations, the whole being composed of carbon, crystals of augite, and the
silicious shields of infusoria. The eruption of carbonic acid gas from
fissures in the Valley of the Magdalene, during the earthquake of New
Granada, on the 16th of November, 1827, suffocated many snakes, rats, and
other animals. Sudden changes of weather, as the occurrence of the rainy
season in the tropics, at an unusual period of the year, have sometimes
succeeded violent earthquakes in Quito and Peru. Do gaseous fluids rise
from the interior of the earth, and mix with the atmosphere? or are these
meteorological processes the action of atmospheric electricity disturbed by
the earthquake? In the tropical regions of America, where sometimes not a
drop of rain falls for ten months together, the natives consider the
repeated shocks of earthquakes, which do not endanger the low reed huts, as
auspicious harbingers of fruitfulness and abundant rain.
p 214
The intimate connection of the phenomena which we have considered is still
hidden in obscurity. Elastic fluids are doublessly the cause of the slight
and perfectly harmless trembling of the earth's surface, which has often
continued several days (as in 1816, at Scaccia, in Sicily, before the
volcanic elevation of the island of Julia), as well as of the terrific
explosions accompanied by loud noise. The focus of this destructive agent,
the seat of the moving force, lies far below the earth's surface; but we
know as little of the extent of this depth as we know of the chemical nature
of these vapors that are so highly compressed. At the edges of two craters,
Vesuvius, and the towering rock which projects beyond the great abyss of
Pichincha, near Quito, I have felt periodic and very regular shocks of
earthquakes, on each occasion from 20 to 30 seconds before the burning
scoriae or gases were erupted. The intensity of the shocks was increased in
proportion to the time intervening between them, and, consequently, to the
length of time in which the vapors were accumulating. This simple fact,
which has been attested by the evidence of so many travelers, furnishes us
with a general solution of the phenomenon, in showing that active volcanoes
are to be considered as safety-valves for the immediate neighborhood. The
danger of earthquakes increases when the openings of the volcano are closed,
and deprived of free communication with the atmosphere; but the destruction
of Lisbon, of Caraccas, of Lima, of Cashmir in 1554,* and of so many cities
of Calabria, Syria, and Asia Minor, shows us, on the whole, that the force
of the shock is not the greatest in the neighborhood of active volcanoes.
[footnote] *On the frequency of earthquakes in Cashmir, see Troyer's German
translation of the ancient 'Radjataringini', vol. ii., p. 297, and Carl
Hugel, 'Reisen', bd. ii., s. 184.
As the impeded activity of the volcano acts upon the shocks of the earth's
surface, so do the latter react on the volcanic phenomena. Openings of
fissures favor the rising of cones of eruption, and the processes which take
place in these cones, by forming a free communication with the atmosphere.
A column of smoke, which had been observed to rise for months together from
the volcano of Pasto, in South America, suddenly disappeared, when on the
4th of February, 1797, the province of Quito, situated at a distance of 192
miles to the south, suffered from the great earthquake of Riobamba. After
the earth had continued to tremble for some time through out the whole of
Syria, in the Cyclades, and in Euboea, the shocks suddenly ceased on the
eruption of a stream of hot mud
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on the Lelantine plains near Chalcia.*
[footnote] * Strabo, lib. i., p. 100, Casaub. That the expression [Greek
words] does not mean erupted mud, but lava, is obvious from a passage in
Strabo, lib. vi., p. 412. Compare Walter, in his 'Abnahme der Vulkanischen
Thatigkeit in Historischen Zeiten' (On the Decrease of Volcanic Activity
during Historical Times), 1844, s. 25.
The intelligent geographer of Amasea, to whom we are indebted for the notice
of this circumstance, further remarks: "Since the craters of Aetna have
been opened, which yield a passage to the escape of fire, and since burning
masses and water have been ejected, the country near the sea-shore has not
been so much shaken as at the time previous to the separation of Sicily from
Lower Italy, when all communications with the external surface were closed."
We thus recognize in earthquakes the existence of a volcanic force, which,
although every where manifested, and as generally diffused as the internal
heat of our planet, attains but rarely, and then only at separate points,
sufficient intensity to exhibit the phenomenon of eruptions. The formation
of veins, that is to say, the filling up of fissures with crystalline masses
bursting forth from the interior (as basalt, melaphyre, and greenstone),
gradually disturbs the free intercommunication of elastic vapors. This
tension acts in three different ways, either in causing disruptions, or
sudden and retroversed elevations, or, finally, as was first observed in a
great part of Sweden, in producing changes in the relative level of the sea
and land, which, although continuous, are only appreciable at intervals of
long period.
Before we leave the important phenomena which we have considered not so much
in their individual characteristics as in their general physical and
geognostical relations, I would advert to the deep and peculiar impression
left on the mind by the first earthquake which we experience, eeven where it
is not attended by any subterranean noise.*
[footnote] *[Dr. Tschudi, in his interesting work, 'Travels in Peru',
translated from the German by Thomasina Ross, p. 170, 1847, describes
strikingly the effect of an earthquake upon the native and upon the
stranger. "No familiarity with the phenomenon can blunt this feeling. The
inhabitant of Lima, who from childhood has frequently witnessed these
convulsions of nature, is roused from his sleep by the shock, and rushes
from his apartment with the cry of 'Misericordia!' The foreigner from the
north of Europe, who knows nothing of earthquakes but by description, waits
with impatience to feel the movement of the earth, and longs to hear with
his own ear the subterranean sounds which he has hitherto considered
fabulous. With levity he treats the apprehension of a coming convulsion,
and laughs at the fears of the natives: but, as soon as his wish is
gratified, he is terror-stricken, and is involuntarily prompted to seek
safety in flight."] -- Tr.
This impression is not,
p 216
in my opinion, the result of a recollection of those fearful pictures of
devastation presented to our imaginations by the historical narratives of
the past, but is rather due to the sudden revelation of the delusive nature
of the inherent faith by which we had clung to a belief in the immobility of
the solid parts of the earth. We are accustomed from early childhood to
draw a contrast between the mobility of water and the immobility of the soil
on which we tread; and this feeling is confirmed by the evidence of our
senses. When, therefore, we suddenly feel the ground move beneath us, a
mysterious and natural force, with which we are previously unacquainted, is
revealed to us as an active disturbance of stability. A moment destroys the
illusion of a whole life; our deceptive faith in the repose of nature
vanishes, and we feel transported, as it were, into a realm of unknown
destructive forces. Every sound -- the faintest motion in the air --
arrests our attention, and we no longer trust the ground on which we stand.
Animals, especially dogs and swine, participate in the same anxious
disquietude; and even the crocodiles of the Orinoco, which are at other
times as dumb as our little lizards, leave the trembling bed of the river,
and run with loud cries into the adjacent forests.
To man the earthquake conveys an idea of some universal and unlimited
danger. We may flee from the crater of a volcano in active eruption, or
from the dwelling whose destruction is threatened by the approach of the
lava stream; but in an earthquake, direct our flight whithersoever we will,
we still feel as if we trod upon the very focus of destruction. This
condition of the mind is not of long duration, although it takes its origin
in the deepest recesses of our nature; and when a series of faint shocks
succeed one another, the inhabitants of the country soon lose every trace of
fear. On the coasts of Peru, where rain and hail are unknown, no less than
the rolling thunder and the flashing lightning, these luminous explosions of
the atmosphere are replaced by the subterranean noises which accompany
earthquakes.*
[footnote] *["Along the whole coast of Peru the atmosphere is almost
uniformly in a state of repose. It is not illuminated by the lightning's
flash, or disturbed by the roar of the thunder; no deluges of rain, no
fierce hurricanes, destroy the fruits of the fields, and with them the hopes
of the husbandman. But the mildness of the elements above ground is
frightfully counterbalanced by their subterranean fury. Lima is frequently
visited by earthquakes, and several times the city has been reduced to a
mass of ruins. At an average, forty-five shocks may be counted on in the
year. Most of them occur in the later part of October, in November,
December, January, May, and June. Experience gives reason to expect the
visitation of two desolating earthquakes in a century. The period between
the two is from forty to sixty years. The most considerable catastrophes
experienced in Lima since Europeans have visited the west coast of South
America happened in the years 1586, 1630, 1687, 1713, 1746, 1806. There is
reason to fear that in the course of a few years this city may be the prey
of another such visitation."] --Tr.
Long habit, and the very
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prevalent opinion that dangerous shocks are only to be apprehended two or
three times in the course of a century, cause faint oscillations of the soil
to be regarded in Lima with scarcely more attention than a hail storm in the
temperate zone.
Having thus taken a general view of the activity -- the inner life, as it
were -- of the Earth, in respect to its internal heat, its electro-magnetic
tension, its emanation of light at the poles, and its irregularly-recurring
phenomena of motion, we will now proceed to the consideration of the
material products, the chemical changes in the earth's surface, and the
composition of the atmosphere, which are all dependent on planetary vital
activity. We see issue from the ground steam and gaseous carbonic acid,
almost always free from the admixture of nitrogen;* carbureted hydrogen gas,
which has been used in the Chinese province Sse-tschuan** for several
thousand years, and recently in the village of Fredonia, in the State of New
York, United States, in cooking and for illumination; sulphureted hydrogen
gas and sulphurous vapors; and, more rarely,*** sulphurous and hydrochloric
acids.****
[footnote] * Bischof's comprehensive work, 'Warmelchere des inneren
Erdkorpers'.
[footnote] **On the Artesian fire-springs (Ho-tsing) in China, and the
ancient use of portable gas (in bamboo canes) in the city of Khiung-tsheu,
see Klaproth, in my 'Asie Centrale', t. iii., p. 519-530.
[footnote] *** Boussingault ('Annales de Chimie', t. lii., p. 181) observed
no evolution of hydrochloric acid from the volcanoes of New Granada, while
Monticelli found it in enormous quantity in the eruption of Vesuvius in 1813.
[footnote] ****[Of the gaseous compounds of sulphur, one, sulphurous acid,
appears to predominate chiefly in volcanoes possessing a certain degree of
activity, while the other, sulphureted hydrogen, has been most frequently
perceived among those in a dormant condition. The occurrence of abundant
exhalations of sulphuric acid, which have been hitherto noticed chiefly in
extinct volcanoes, as for instance, in a stream issuing from that of Purace,
between Bogota and Quito, from extinct volcanoes in Java, is satisfactorily
explained in a recent paper by M. Dumas, 'Annales de Chimie', Dec., 1846.
He shows that when sulphureted hydrogen, at a temperature above 100 degrees
Fahr., and still better when near 190 degrees, comes in contact with certain
porous bodies, a catalytic action is set up, by which water, sulphuric acid,
and sulphur are produced. Hence probably the vast deposits of sulphur,
associated with sulphates of lime and strontian, which are met with in the
western parts of Sicily.] -- Tr.
Such effusions
p 218
from the fissures of the earth not only occur in the districts of still
burning or long-extinguished volcanoes, but they may likewise be observed
occasionally in districts where neither trachyte nor any other volcanic
rocks are exposed on the earth's surface. In the chain of Quindiu I have
seen sulphur deposited in mica slate from warm sulphurous vapor at an
elevation of 6832 feet* above the level of the sea, while the same species
of rock, which was formerly regarded as primitive, contains, in the Cerro
Cuello, near Tiscan, south of Quito, an immense deposit of sulphur imbedded
in pure quartz.
[footnote] * Humboldt, 'Recucil d'Observ. Astronomiques', t. i., p. 311
('Nivellement Barometrique de la Cordillere des Andes', No. 206).
Exhalations of carbonic acid ('mofettes') are even in our days to be
considered as the most important of all gaseous emanations, with respect to
their number and the amount of their effusion. We see in Germany, in the
deep valleys of the Eifel, in the neighborhood of the Lake of Laach,* in the
crater-like valley of the Wehr and in Western Bohemia, exhalations of
carbonic acid gas manifest themselves as the last efforts of volcanic
activity in or near the foci of an earlier world.
[footnote] *[The Lake of Laach, in the district of the Eifel, is an expanse
of water two miles in circumference. The thickness of the vegetation on the
sides of its crater-like basin renders it difficult to discover the nature
of the subjacent rock, but it is probably composed of black cellular augitic
lava. The sides of the crater present numerous loose masses, which appear
to have been ejected, and consist of glassy feldspar, ice-spar, sodalite,
hauyne, spinellane, and leucite. The resemblance between these products and
the masses formerly ejected from Vesuvius is most remarkable. (Daubeney 'On
Volcanoes', p. 81.) Dr. Hibbert regards the Lake of Laach as formed in the
first instance by a crack caused by the cooling of the crust of the earth,
which was widened afterward into a circular cavity by the expansive force of
elastic vapors. See 'History of the Extinct Volcanoes of the Basin of
Neuwied', 1832.] -- Tr.
In those earlier periods, when a higher terrestrial temperature existed, and
when a great number of fissures still remained unfilled, the processes we
have described acted more powerfully, and carbonic acid and hot steam were
mixed in larger quantities in the atmosphere, from whence it follows, as
Adolph Bronguiart has ingeniously shown,* that the primitive vegetable world
must have exhibited almost every where, and independently of geographical
position, the most luxurious abundance and the fullest development of
organism.
[footnote] *Adolph Bronguiart, in the 'Annales des Sciences Naturelles', t.
xv., p. 225.
In these constantly warm and damp atmospheric strata, saturated with
p 219
carbonic acid, vegetation must have attained a degree of vital activity, and
derived the superabundance of nutrition necessary to furnish materials for
the formation of the beds of lignite (coal) constituting the inexhaustible
means on which are based the physical power and prosperity of nations. Such
masses are distributed in basins over certain parts of Europe, occurring in
large quantities in the British Islands, in Belgium, in France, in the
provinces of the Lower Rhine, and in Upper Silesia. At the same primitive
period of universal volcanic activity, those enormous quantities of carbon
must also have escaped from the earth which are contained in limestone
rocks, and which, if seprated from oxygen and reduced to a solid form, would
constitute about the eighth part of the absolute bulk of these mountain
masses.*
[footnote] * Bischof, op. cit., s. 324, Anm. 2.
That portion of the carbon which was not taken up by alkaline earths, but
remained mixed with the atmosphere, as carbonic acid, was gradually consumed
by the vegetation of the earlier stages of processes of vegetable life, only
retained the small quantity which it now possesses, and which is not
injurious to the sulphurous vapor have occasioned the destruction of the
species of mollusca and fish which inhabited the inland waters of the
earlier world, and have given rise to the formation of the contorted beds of
gypsum, which have doubtless been frequently affected by shocks of
earthquakes.
Gaseous and liquid fluids, mud, and molten earths, ejected from the craters
of volcanoes, which are themselves only a kind of "intermittent springs,"
rise from the earth under precisely analogous physical relations.*
[footnote] *Humboldt, 'Asie Centrale', t. i., p. 43.
All these substances owe their temperature and their chemical character to
the place of their origin. The 'mean' temperature of aqueous springs is
less than that of the air at the point whence they emerge, if the water flow
from a height; but their heat increases with the depth of the strata with
which they are in contact at their origin. We have already spoken of the
numerical law regulating this increase. The blending of waters that have
come from the height of a mountain with those that have sprung from the
depths of the earth, render it difficult to determine the position of the
'isogeothermal lines'* (lines of equal internal
p 220
terrestrial temperature, when this determination is to be made from the
temperature of flowing springs.
[footnote] *On the theory of isogeothermal (chthonisothermal) lines,
consult the ingenious labors of Kupffer, in Pogg, 'Annalen', bd xv., s. 184,
and bd xxxii., s. 270, in the 'Voyage dans l'Oural', p. 382-298, and in the
'Edinburgh Journal of Science', New Series, vol. iv., p. 355. See, also,
Kamtz, 'Lehrb. der Meteor.', bd. ii., s. 217; and, on the ascent of the
chthonisothermal lines in mountainous districts, Bischof, s. 174-198.
Such at any rate, is the result I have arrived at from my own observations
and those of my fellow-travelers in Northern Asia. The temperature of
springs, which has become the subject of such continuous physical
investigation during the last half century, depends, like the elevation of
the line of perpetual snow, on very many simultaneous and deeply-involved
causes. It is a function of the temperature of the stratum in which they
take their rise, of the specific heat of the soil, and of the quantity and
temperature of the meteoric water,* which is itself different from the
temperature of the lower strata of the atmosphere, according to the
different modes of its origin in rain, snow, or hail.**
[footnote] *Leop. v. Buch, in Pogg., 'Annalen', bd. xii., s. 405.
[footnote] ** On the temperature of the drops, of rain in Cumana, which
fell to 72 degrees, when the temperature of the air shortly before had been
86 degrees and 88 degrees, and during the rain sank to 74 degrees, see my
'Relat. Hist.', t. ii., p. 22. The rain-drops, while falling, change the
normal temperature they originally possessed, which depends on the height of
the clouds from which they fell, and their heating on their upper surface by
the solar rays. The rain-drops, on their first production, have a higher
temperature than the surrounding medium in the superior strata of our
atmosphere, in consequence of the liberation of their latent heat; and they
continue to rise in temperature, since, in falling through lower and warmer
strata, vapor is precipitated on them, and they thus increase in size
(Bischof, 'Warmelehre des inneren Erdkorpers' s. 73); but this additional
heating is compensated for by evaporation. The cooling of the air by rain
(putting out of the question what probably belongs to the electric process
in storms) is effected by the drops, which are themselves of lower
temperature, in consequence of the cold situation in which they were formed,
and bring down with them a portion of the higher colder air, and which
finally, by moistening the ground, give rise to evaporation. The cooling of
the air by rain (putting out of the question what probably belongs to the
electric process in storms) is effected by the drops, which are themselves
of lower temperature, in consequence of the cold situation in which they
were formed, and bringi down with them a portion of the higher colder air,
and which finally, by moistening the ground, give rise to evaporation.
These are the ordinary relations of the phenomenon. When, as occasionally
happens, the rain-drops are warmer than the lower strata of the atmosphere
(Humboldt, 'Rel. Hist.', t. iii., p. 513), the cause must probably be sought
in higher warmer currents, or in a higher temperature of widely-extended and
not very thick clouds, from the action of the sun's rays. How, moreover,
the phenomenon of supplementary rainbows, which are explained by the
interference of light, is connected with the original and increasing size of
the falling drops, and how an optical phenomenon, if we know how to observe
it accurately, may enlighten us regarding a meteorological process,
according to diversity of zone, has been shown, with much talent and
ingenuity, by Arago, in the 'Annuaire' for 1836, p. 300.