CURIOSITIES RESPECTING EARTHQUAKES.

Earthquakes and their Causes.—From A. de Humboldt’s Personal Narrative of Travels, translated by Helen Maria Williams.

“It is a very old and commonly received opinion at Cumana, Acapulca, and Lima, that a perceptible connection exists between earthquakes, and the state of the atmosphere that precedes these phenomena. On the coast of New Andalusia, the inhabitants are alarmed, when, in excessively hot weather, and after long droughts, the breeze suddenly ceases to blow, and the sky, clear and without clouds at the zenith, exhibits near the horizon, at six or eight degrees elevation, the appearance of a reddish vapour. These prognostics are however very uncertain; and when the whole of the meteorological variations, at the times when the globe has been the most agitated, are called to mind, it is found, that violent shocks take place equally in dry and in wet weather, when the coolest winds blow, or during a dead and suffocating calm. From the great number of earthquakes, which I have witnessed to the north and south of the equator; on the continent, and in the bason of the seas; on the coasts, and at 2500 toises height; it appears to me, that the oscillations are generally very independent of the previous state of the atmosphere. This opinion is embraced by a number of enlightened persons, who inhabit the Spanish colonies; and whose experience extends, if not over a greater space of the globe, at least to a greater number of years than mine. On the contrary, in parts of Europe where earthquakes are rare compared to America, natural philosophers are inclined to admit an intimate connection between the undulations of the ground, and certain meteors, which usually take place at the same epocha. In Italy, for instance, the sirocco and earthquakes are suspected to have some connection; and at London, the frequency of falling stars, and those southern lights which have since been often observed by Mr. Dalton, were considered as the forerunners of those shocks which were felt from 1748 to 1756.

EFFECTS OF AN EARTHQUAKE.—Page 499.

The engraving represents the great earthquake of 1755, in which the city of Lisbon,
in Portugal, was entirely destroyed, and 20,000 persons were killed.

SAND STORM OR SAND FLOOD IN THE DESERTS OF ARABIA.—Page 521.

In these terrible whirlwinds of sand, whole caravans are sometimes overwhelmed and destroyed.

“On the days when the earth is agitated by violent shocks, the regularity of the horary variations of the barometer is not disturbed under the tropics. I have verified this observation at Cumana, at Lima, and at Riobamba; and it is so much the more worthy of fixing the attention of natural philosophers, as in St. Domingo, at the town of Cape FranÇois, it is asserted that a water barometer was observed to sink two inches and a half immediately before the earthquake of 1770. It is also related, that at the time of the destruction of Oran, a druggist fled with his family, because, observing accidentally, a few minutes before the earthquake, the height of the mercury in his barometer, he perceived that the column sunk in an extraordinary manner. I know not whether we can give credit to this assertion: but as it is nearly impossible to examine the variations of the weight of the atmosphere during the shocks, we must be satisfied in observing the barometer before or after these phenomena have taken place. In the temperate zone, the aurora borealis does not always modify the variation of the needle, and the intensity of the magnetic forces: perhaps also earthquakes do not act constantly in the same manner on the air that surrounds us.

“We can scarcely doubt, that the earth, when opened and agitated by shocks, occasionally sends forth gaseous exhalations through the atmosphere, in places remote from the mouths of volcanoes not extinct. At Cumana, as we have already observed, flames and vapours, mixed with sulphureous acid, spring up from the most arid soil. In other parts of the same province, the earth ejects water and petroleum. At Riobamba, a muddy and inflammable mass, which is called moya, issues from crevices that close again, and accumulates into elevated hills. At seven leagues from Lisbon, near Colares, during the terrible earthquake of the 1st of November, 1755, flames, and a column of thick smoke, were seen to issue from the flanks of the rocks of Alvidras, and, according to some witnesses, from the bosom of the sea. This smoke lasted several days, and it was the more abundant in proportion as the subterraneous noise, which accompanied the shocks, was louder.

“Elastic fluids thrown into the atmosphere may act locally on the barometer, not by their mass, which is very small compared to the mass of the atmosphere; but because, at the moment of the great explosions, an ascending current is probably formed, which diminishes the pressure of the air. I am inclined to think, that in the greater number of earthquakes, nothing escapes from the agitated earth, and that, when gaseous exhalations and vapours take place, they oftener accompany or follow, than precede, the shocks. This last circumstance explains a fact, which seems indubitable; I mean that mysterious influence, in equinoctial America, of earthquakes accompanying a change of climate, and the order of the dry and rainy seasons. If the earth generally acts on the air only at the moment of the shocks, we can conceive why it is so rare that a sensible meteorological change becomes the presage of these great revolutions of nature.

“The hypothesis, according to which, in the earthquakes of Cumana, elastic fluids escape from the surface of the soil, seems confirmed by the observation of the dreadful noise which is heard during the shocks at the borders of the wells in the plain of Charas. Water and sand are sometimes thrown out twenty feet high. Similar phenomena have not escaped the observation of the ancient inhabitants of Greece and Asia Minor, abounding with caverns, crevices, and subterraneous rivers. Nature, in its uniform progress, every where suggests the same ideas of the causes of earthquakes, and the means by which man, forgetting the measure of his strength, pretends to diminish the effect of the subterraneous explosions. What a great Roman naturalist has said of the utility of wells and caverns, is repeated in the New World by the most ignorant Indians of Quito, when they shew travellers the guaicos, or crevices of Pichincha.

“The subterraneous noise, so frequent during earthquakes, is generally not in the ratio of the strength of the shocks. At Cumana it constantly precedes them; while at Quito, and lately at Caraccas, and in the West India Islands, a noise like the discharge of a battery was heard a long time after the shocks had ceased. A third kind of phenomenon, the most remarkable of the whole, is the rolling of those subterraneous thunders, which last several months, without being accompanied by the least oscillating motion of the ground.

“In every country subject to earthquakes, the point where (probably by a disposition of the stony strata) the effects are the most sensible, is considered as the cause and the focus of the shocks. Thus, at Cumana, the hill of the castle of St. Antonio, and particularly the eminence on which the convent of St. Francis is placed, are believed to contain an enormous quantity of sulphur, and other inflammable matter. We forget, that the rapidity with which the undulations are propagated to great distances, even across the basin of the ocean, proves that the centre of action is very remote from the surface of the globe. From this same cause, no doubt, earthquakes are not restrained to certain species of rocks, as some naturalists pretend, but all are fitted to propagate the movement. In order to keep within the limits of my own experience, I shall here cite the granites of Lima and Acapulco; the gneiss of Caraccas; the mica-slate of the peninsula of Araya; the primitive thonschiefer of Tepecuacuilco, in Mexico; the secondary limestones of the Apennines; Spain, and new Andalusia; and finally, the trappean porphyries of Quito and Popayan. In these different places the ground is frequently agitated by the most violent shocks; but sometimes, in the same rock, the superior strata form invincible obstacles to the propagation of the motion. Thus, in the mines of Saxony, we have seen workmen hasten up, affrighted by oscillations which were not felt at the surface of the ground.

“If, in regions the most remote from each other, primitive, secondary, and volcanic rock, share equally in the convulsive movements of the globe; we cannot but admire also, that in ground of little extent, certain classes of rocks oppose themselves to the propagation of the shocks. At Cumana, for instance, before the catastrophe of 1797, the earthquakes were felt only along the southern and calcareous coast of the gulf of Cariaco, as far as the town of this name; while in the peninsula of Araya, and at the village of Marinaquez, the ground did not partake of the same agitation. The inhabitants of this northern coast, which is composed of mica-slate, built their huts on a motionless earth; a gulf three or four thousand fathoms in breadth separated them from a plain covered with ruins, and overturned by earthquakes. This security, founded on the experience of several ages, has vanished; and since the fourteenth of December, 1797, new communications appear to have been opened in the interior of the globe. At present the peninsula of Araya is not merely subject to the agitation of the soil of Cumana; the promontory of mica-slate is become in its turn a particular centre of the movements. The earth is sometimes strongly shaken at the village of Marinaquez, when on the coast of Cumana the inhabitants enjoy the most perfect tranquillity. The gulf of Cariaco nevertheless is only sixty or eighty fathoms deep.

“It is thought, from observations made both on the continent and in the islands, that the western and southern coasts are most exposed to shocks. This observation is connected with the ideas which geologists have long formed of the position of the high chains of mountains, and the direction of their steepest declivities: the volcanic phenomena of the Cordilleras and Caraccas, and the frequency of the oscillations on the eastern and northern coast of Terra Firma, in the gulf of Paria, at Carupano, at Cariaco, and at Cumana, are proofs of the certainty of this opinion. In New Andalusia, as well as in Chili and Peru, the shocks follow the course of the shore, and extend but little inland. This circumstance, as we shall soon find, indicates an intimate connection between the causes that produce earthquakes and volcanic eruptions. If the earth was most agitated on the coasts, because they are the lowest part of the land, why should not the oscillations be equally strong and frequent on those vast savannas or meadows, which are scarcely eight or ten toises above the level of the ocean?

“The earthquakes of Cumana are connected with those of the West India Islands; and it has even been suspected, that they have some connection with the volcanic phenomena of the Cordilleras of the Andes. On the fourth of November, 1797, the soil of the province of Quito underwent such a destructive commotion, that, notwithstanding the extreme thinness of the population of that country, near forty thousand natives perished, buried under the ruins of their houses, swallowed up in the crevices, or drowned in lakes that were suddenly formed. At the same period, the inhabitants of the eastern Antilles were alarmed by shocks, which continued during eight months, when the volcano of Guadaloupe threw out pumice stones, ashes, and gusts of sulphureous vapours. This eruption of the twenty-seventh of September, during which very long-continued subterraneous noises were heard, was followed on the fourteenth of December by the great earthquake of Cumana. Another volcano of the West India Islands, that of St. Vincent’s, has lately given a fresh instance of these extraordinary connections. This volcano had not emitted flames since 1718, when they burst forth anew, in 1812. The total ruin of the city of Caraccas preceded this explosion thirty-five days, and violent oscillations of the ground were felt, both in the islands, and on the coasts of Terra Firma.

“It has long been remarked, that the effects of great earthquakes extend much farther than the phenomena arising from burning volcanoes. In studying the physical revolutions of Italy, and carefully examining the series of the eruptions of Vesuvius and Etna, we can scarcely recognize, notwithstanding the proximity of these mountains, any traces of simultaneous action. It is, on the contrary, undeniable, that at the period of the last and preceding destruction of Lisbon, the sea was violently agitated even as far as the New World, for instance, at the island of Barbadoes, more than twelve hundred leagues distant from the coasts of Portugal.

“Several facts tend to prove, that the causes which produce earthquakes have a near connection with those that act in volcanic eruptions. We learnt at Pasto, that the column of black and thick smoke, which in 1797 issued for several months from the volcano near this shore, disappeared at the very hour when, sixty leagues to the south, the towns of Riobamba, Hambato, and Tacunga, were overturned by an enormous shock. When, in the interior of a burning crater, we are seated near those hillocks formed by ejections of scoria and ashes, we feel the motion of the ground several seconds before each partial eruption takes place. We observed this phenomenon at Vesuvius in 1805, while the mountain threw out scoria; we were witnesses of it in 1812, on the brink of the immense crater of Pichincha, from which nevertheless at that time clouds of sulphureous acid vapours only issued.

“Every thing in earthquakes seems to indicate the action of elastic fluids seeking an outlet to spread themselves in the atmosphere. Often, on the coasts of the South Sea, the action is almost instantaneously communicated from Chili to the gulf of Guayaquil, a distance of six hundred leagues; and, what is very remarkable, the shocks appear to be so much the stronger, as the country is more distant from burning volcanoes. The granitic mountains of Calabria, covered with very recent breccia, the calcareous chain of the Apennines, the country of Pignerol, the coasts of Portugal and Greece, and those of Peru and Terra Firma, afford striking proofs of this assertion. The globe, it may be said, is agitated with greater force, in proportion as the surface has a smaller number of funnels communicating with the caverns of the interior. At Naples and Messina, at the foot of Cotopaxi and of Tunguragua, earthquakes are dreaded only when vapours and flames do not issue from the crater. In the kingdom of Quito, the great catastrophe of Riobamba, which we have before mentioned, has led several well-informed persons to think, that this unfortunate country would be less often desolate, if the subterraneous fire would break the porphyritic dome of Chimborazo; and this colossal mountain should become a burning volcano. At all times analogous facts have led to the same hypothesis. The Greeks, who, like ourselves, attributed the oscillations of the ground to the action of elastic fluids, cited, in favour of their opinion, the total cessation of the shocks at the island of Euboea, by the opening of a crevice in the Lelantine plain.”

The following is an account of an Earthquake of Caraccas; by M. Palacio Faxar:—

“The ridge of mountains, which branches out from the Andes near the isthmus of Panama, and which, taking the direction of the eastern coast, crosses part of New Granada and Venezuela, seems to have been the seat of that earthquake, which, on the 26th March, 1812, destroyed many populous towns of the province of Caraccas. It is this branch of the Cordilleras, that forms the Sierra-nevada of Chita, that of Merida de Maracaybo, and the height called La Silla de Caracca; and it is between these three remarkable points that the gold mines of Pamplona, the mineral water of Merida de Maracaybo, and the copper mines of Aroa, are found. Between the picturesque Sierra-nevada of Merida de Maracaybo, and La Silla de Caracca, where spring is perpetual, the earthquake was most strongly felt.

“At the south-east of this ridge of mountains, there are plains of an immense extent, covered with different species of grasses, and watered by innumerable torrents, which falling from the mountains, and uniting in different bodies, majestically enter the Orinoco. These plains were likewise convulsed for above 120 leagues in Venezuela: the towns situate immediately at the foot of the Cordilliera, or in the valleys between them, suffered most severely: those seated in the plains did not suffer considerable injury, though violently shaken. For five months a continued drought had parched the earth, no rain having fallen, and in the preceding month of December, a slight shock of an earthquake had been felt at Caraccas. It was on the eve of the Crucifixion, when Catholics assembled together in their churches, to commemorate, with public prayers and processions, the sufferings and merits of their Redeemer, that this sad catastrophe had happened. The weather was fine, and the air serene, when between four and five P. M. a hollow sound like the roar of a cannon was heard, which was followed by a violent oscillatory motion from west to east, which lasted about seventeen seconds, and which stopped all the public clocks; the convulsion diminished for some moments, but was succeeded by a more violent shock than the first, for nearly twenty seconds, keeping the same direction; a calm followed, which lasted about fourteen seconds, after which, a most alarming trepidation of the earth took place for fifteen seconds: the total duration about one minute and fifteen seconds. The inhabitants of Caraccas, struck with terror, unitedly and loudly implored the protection of Heaven: some ran wildly through the streets; some remained immoveable with astonishment; while others, crowding into the churches, sought refuge at the foot of the altar. The crash of falling buildings, the clouds of dust which filled the air, and the anxious cries of mothers, who inquired in vain for their children lost in the tumult, increased the horrors of this sad day. To this scene of disorder succeeded the most horrible despair. Dead bodies, wounded persons crying for protection, presented themselves every where to those who had escaped from the catastrophe, and who could not turn their eyes from these objects of pity and horror, without meeting with heaps of ruin, which had buried hundreds of unfortunate persons, whose lamentations uselessly pierced their hearts, for it was impossible to give relief or assistance to all.

“It has been computed, that in this calamitous day, near 20,000 persons perished at Venezuela. A great part of the veteran troops were of this number; and all the arms destined for the defence of their country, were buried under the ruins of the barracks. The towns of Caraccas, Merida de Maracaybo, and Laguaira, were totally destroyed; those of Barquirineto, Sanfelipe, and others, suffered considerably. It is to be remarked, that Truxillo, which is situate between Merida de Maracaybo and Sanfelipe, experienced very little damage. At the last place, near the mines of Aroa, the first signal they had of the earthquake was an electric shock, which deprived many persons of their power of motion; and in Valencia, Caraccas, and the neighbouring country, the inhabitants were, for about twenty days after the earthquake, in an extraordinary state of irritability. Many persons, who suffered from intermittent fevers, recovered immediately, in consequence of the effect of the earthquake.

“At Vallecillo, near Valencia, a rivulet spouted out from a hill, which continued to flow for some hours after the earthquake, and which I visited a few days after. The river Guaire, which runs through the valley of Caraccas, was greatly swelled soon after the earthquake, and remained in that state for several days. The water of the bay of Maracaybo withdrew considerably, and it is said that the mountain Avila, which separates Caraccas from Laguaira, sunk several feet into the earth.

“The earthquakes continued for many days, we may say, without interruption: they diminished as it were by degrees, though the last were remarkably strong. So late as the month of October in the same year, there was a violent shock. The earthquake of the 26th March was felt at SantafÉ de BogotÁ, and even at Carthagena, though it was very little felt at Cumana.

“In the following April, a volcano burst out in the island of St. Vincent. About the time of the eruption, a noise like that occasioned by the discharge of a cannon was heard at Caraccas and Laguaira, which caused a general alarm, the inhabitants of each place supposing that the neighbouring town was attacked by the enemy. This roaring noise was distinctly heard where the river Nula falls into the Apure, which is more than 100 leagues from Caraccas. In the same year, 1812, many strong shocks of an earthquake were felt at Samaica and CuraÇoa.

“The earthquake of the 26th March alarmed so deeply the inhabitants of Venezuela, that they expected to see the earth open and swallow them at every convulsion; and as it happened on the anniversary of their political revolution, they supposed that event had incurred the displeasure of the Almighty. The clergy, who were enemies to the revolution, as their privileges had been diminished by the new constitution of Venezuela, availed themselves of the disposition of the people, and preached every where against the new republic. Such was the beginning of the civil war at Venezuela; a war, which has desolated those beautiful countries, and which has destroyed the tenth part of their population.”

The celebrated poet Cowper, in the second book of his admirable poem, The Task, has given us a very accurate and sublime description of the effects of Earthquakes, from which the following is an extract:—

The rocks fall headlong, and the valleys rise,
The rivers die into offensive pools,
And, charg’d with putrid verdure, breathe a gross
And mortal nuisance into all the air.
What solid was, by transformation strange,
Grows fluid; and the fixt and rooted earth,
Tormented into billows, heaves and swells,
Or with vortiginous and hideous whirl
Sucks down its prey insatiable. Immense
The tumult and the overthrow, the pangs
And agonies of human and of brute
Multitudes, fugitive on ev’ry side,
And fugitive in vain. The sylvan scene
Migrates uplifted; and, with all its soil,
Alighting on far distant fields, finds out
A new possessor, and survives the change.
Ocean has caught the frenzy, and, upwrought
To an enormous and o’erbearing height,
Not by a mighty wind, but by that voice
Which winds and waves obey, invades the shore
Resistless. Never such a sudden flood,
Upridg’d so high, and sent on such a charge,
Possess’d an inland scene. Where now the throng
That press’d the beach, and, hasty to depart,
Look’d to the sea for safety? They are gone,
Gone with the refluent wave into the deep—
A prince with half his people.

It is a consolation to every good man, to consider that the world is governed by a wise and good, as well as powerful Being, who gives liberty to the powers of nature to range, or restrains them, as may best suit his divine purposes; which have always the ultimate good of the whole creation in view.