Digitale Ausgabe

The grand catastrophe in which this volcanic mountainLarge hillthrown up by avolcano in1759. issued from the earth, and by which the face of a consi-derable extent of ground was totally altered, was perhapsone of the most extensive physical changes, that the historyof our globe exhibits. Geology points out spots in theocean, where, within the last two thousand years, volcanicislets have arisen above the surface of the sea, as near the Azores, in the Archipelago, and on the south of Iceland:but it records no instance of a mountain of scoriæ andashes, 517 met. [563 yards] above the old level of theneighbouring plains, suddenly formed in the centre of athousand small burning cones, thirty-six leagues from theseashore, and forty-two leagues from any other volcano.This phenomenon remained unknown to the mineralogistsand natural philosophers of Europe, though it took place

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* Extracted from his Essay on New Spain. Journal de Physique,vol. LXIX, p. 149.|82| but fifty years ago, and within six days journey of the capi-tal of Mexico. Country de-scribed. Descending from the central flat toward the coasts of thePacific ocean, a vast plain extends from the hills of Agua-sarco to the villages of Toipa, and Patatlan, equally cele-lebrated for their fine cotton plantations. Between thepicachos del Mortero and the cerras de las Cuevas and deCuiche, this plain is only from 750 to 800 met. [820 to 880yards] above the level of the sea. Basaltic hills rise in themidst of a country, in which porphyry with base of green-stone predominates. Their summits are crowned with oaksalways in verdure, and the foliage of laurels and olives in-termingled with dwarf fan palms. This beautiful vegeta-tion forms a singular contrast with the arid plain, whichhas been laid waste by volcanic fire. A fertile plain To the middle of the eighteenth century fields of sugar-canes and indigo extended between two rivulets, called Cui-timba and San Pedro. They were skirted by basalticmountains, the structure of which seems to indicate, thatall the country, in remote periods, has several times expe-rienced the violent action of volcanoes. These fields, irri-gated by art, belonged to the estate of San Pedro de Jo-rullo (Xorullo, or Juvriso), one of the largest and most shaken by anearthquake,valuable in the country. In the month of June, 1759, fear-ful rumbling noises were accompanied with frequent shocksof an earthquake, which succeeded each other at intervalsfor fifty or sixty days, and threw the inhabitants of the es-tate into the greatest consternation. From the beginningof the month of September, every thing seemed perfectlyquiet, when in the night of the 28th of that month a terri-ble subterranean noise was heard anew. The frightenedIndians fled to the mountains of Aguasarco. A space of and a hill rais-ed on it.three or four square miles, known by the name of Malpays,rose in the shape of a bladder. The boundaries of thisrising are still distinguishable in the ruptured strata. TheMalpays towards the edge is only 12 met. [13 yards] abovethe former level of the plain, called las playas de Jorullo;but the convexity of the ground increases progressivelytoward the centre, till it reaches the height of 160 met.[175 yards]. |83| They who witnessed this grand catastrophe from the topThe event de-scribed. of Aguasarco assert, that they saw flames issue out of theground for the space of more than half a league square;that fragments of red hot rocks were thrown to a prodigiousheight; and that through a thick cloud of ashes, illuminedby the volcanic fire, and resembling a stormy sea, the soft-ened crust of the earth was seen to swell up. The riversof Cuitimba and San Pedro then precipitated themselvesinto the burning crevices. The decomposition of the watercontributed to reanimate the flames, which were percepti-ble at the city of Pascuoro, though standing on a very wideplain 1400 met. [1530 yards] above the level of the playasde Jorullo. Eruptions of mud, particularly of the strataof clay including decomposed nodules of basaltes with con-centric layers, seem to prove, that subterranean waters hadno small part in this extraordinary revolution. Thousandsof small cones, only two or three yards high, which theIndians call ovens, issued from the raised dome of the Mal-pays. Though the heat of these volcanic ovens has dimi-nished greatly within these fifteen years, according to thetestimony of the Indians, I found the thermometer rise to95° [if centig. 203° F.] in the crevices that emitted anaqueous vapour. Each little cone is a chimney, from whicha thick smoke rises to the height of ten or fifteen met. [11or 16 yards]. In several a subterranean noise is heard likethat of some fluid boiling at no great depth. Amid these ovens, in a fissure, the direction of which isSix large hillsin one line. from N. N. E. to S. S. E., six large hummocks rise 400or 500 met. [440 or 550 yards] above the old level of theplain. This is the phenomenon of Monte Novo at Naplesrepeated several times in a row of volcanic hills. The lof-tiest of these huge hummocks, which reminded me of thecountry of Auvergne, is the large volcano of Jorullo. Itis constantly burning, and has thrown out on the north sidean immense quantity of scorified and basaltic lava, includ-ing fragments of primitive rocks. These grand eruptionsof the central volcano continued till February, 1760. Inthe succeeding years they became gradually less frequent.The Indians, alarmed by the horrible noise of the new vol-cano, at first deserted the villages for seven or eight leagues |84| round the plain of Jorullo. In a few months they becamefamiliar with the alarming sight, returned to their huts,and went down to the mountains of Aguasarco and SantaInes, to admire the sheaves of fire thrown out by an infi-nite number of large and small volcanic openings. The Ashes carriedto a great dis-tance.ashes then covered the houses of Queretoro, more than 48leagues [120 miles] in a right line from the place of the ex-plosion. Though the subterranean fire appears to be in nogreat activity * at present, and the Malpays and the greatvolcano begin to be covered with vegetables, we found the The air stillheated by thesubterraneanfire.air so heated by the little ovens, that in the shade, and at aconsiderable distance from the ground, the thermometerrose to 43° [109·4° F.]. This fact evinces, that there is noexaggeration in the report of some of the old Indians, whosay, that the plains of Jorullo were uninhabitable for seve-ral years, and even to a considerable distance from theground raised up, on account of the excessive heat. Two rivers lost, Near the cerro of Santa Ines the traveller is still shownthe rivers of Cuitimba and San Pedro, the limpid watersof which formerly refreshed the sugarcanes on the estateof Don Andrew Pimantel. These springs were lost in the and supposed to appear again much heated.night of the 29th of September, 1759: but 2000 met.[near 2200 yards] to the westward, in the soil that has beenelevated, two rivulets are seen to break out of the clayeydome of the furnaces, exhibiting themselves as thermalwaters, in which the thermometer rises to 52·7° [126·86° F.].The Indians still give these the names of San Pedro andCuitimba, because in several parts of the Malpays largebodies of water are supposed to be heard running from eastto west, from the mountains of Santa Ines to the estate ofthe Presentation. Near this estate is a brook, that emits Sulphurouswater.sulphuretted hidrogen gas: it is more than 7 met. [near 8yards] wide, and is the most copious hidrosulphurous springI ever saw.

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* In the bottom of the crater we found the heat of the air 47°[116·6° F.], and in some places 58° and 60° [136·4° and 140°]. Wehad to pass over cracks exhaling sulphurous vapours, in which thethermometer rose to 85° [185°]. From these cracks, and the heapsof scoriæ that cover considerable hollows, the descent into the crateris not without danger.|85| In the opinion of the natives these extraordinary changesThe catastro-phe supposedowing to thevengeance ofsome monks. I have described, the crust of earth raised and cracked byvolcanic fire, the mountains of scoriæ and ashes heaped up,are the works of monks; the greatest, no doubt, they everproduced in either hemisphere. Our Indian host, at thehut we inhabited in the plain of Jorullo, told us, that somemissionary capuchins preached at the estate of San Pedro,and, not meeting a favourable reception, uttered the mosthorrible and complicated imprecations against this plain,then so beautiful and fertile. They prophesied, that theestate should first be swallowed up by flames issuing out ofthe bowels of the Earth; and that the air should afterwardbe cooled to such a degree, that the neighbouring moun-tains should remain for ever covered with ice and snow.The first of these maledictions having been so fatally veri-fied, the common people foresee in the gradual cooling ofthe volcano the presage of a perpetual winter. I havethought it right to mention this vulgar tradition, worthy aplace in the epic poem of the jesuit Landivar, because itexhibits a striking feature of the manners and prejudicesof these remote countries. It shows the active industry ofa class of men, who, too frequently abusing the credulityof the people, and pretending to possess the power of sus-pending the immutable laws of nature, know how to availthemselves of every event for establishing their empire bythe fear of physical evil. The situation of the new volcano of Jorullo leads to aLine of volca-noes in Mexicocrossing thechain of hills. very curious geological observation. It has already beenobserved in the 3d chapter, that there is in New Spain aline of great heights, or a narrow zone included betweenthe latitudes of 18° 59′ and 19° 12′, in which are all thesummits of Anahuac that rise above the region of perpetualsnow. These summits are either volcanoes still actuallyburning; or mountains, the form of which, as well as thenature of their rocks, renders it extremely probable, thatthey formerly contained subterranean fire. Setting outfrom the coast of the Gulf of Mexico, and proceeding west-ward, we find the peak of Oribaza, the two volcanoes ofla Puebla, the Nevado de Toluca, the peak of Tancitaro,and the volcano of Colima. These great heights, instead |86| of forming the ridge of the cordillera of Anahuac, and fol-lowing its direction, which is from S. E. to N. W., are onthe contrary in a line perpendicular to the axis of the greatchain of mountains. It is certainly worthy remark, that inthe year 1759 the new volcano of Jorullo was formed in thecontinuation of this line, and on the same parallel as theancient Mexican volcanoes. Indicate a longinterior fissurein the Earth. A view of my plan of the environs of Jorullo will show,that the six large hummocks have risen out of the earth ona vein, that crosses the plain from the cerro of las Cuevasto the pichaco del Montero. The new mouths of Vesuviustoo are found ranged along a fissure. Do not these analo-gies give us reason to suppose, that there exists in this partof Mexico, at a great depth within the Earth, a fissurestretching from east to west through a space of 137 leagues[343 miles], and through which the volcanic fire has madeits way at different times, bursting the outer crust of por-phyritic rocks, from the coasts of the Gulf of Mexico tothe South Sea? Is this fissure prolonged to that littlegroupe of islands, called by Collnet the Archipelago ofRegigedo, and round which, in the same parallel with theMexican volcanoes, pumice stone has been seen floating?Naturalists who distinguish the facts offered by descriptivemineralogy from theoretical reveries concerning the primi-tive state of our planet will pardon me for having consignedthese observations to the general Map of New Spain, con-tained in the Mexican Atlas.