buried in the entrails of the Earth; but if the narrow circle, in which all certain traditions are confined, do not present any of those general revolutions, which have heaved up the Cordilleras, and buried myriads of pelagian animals, Nature, acting under our eyes, does not less exhibit tumultuous though partial changes, the study of which may throw light on the most remote epochs. Those mysterious powers reside in the interior of the Earth, the effects of which are manifested at the surface by the production of vapours, of incandescent slags, of new volcanic rocks and thermal springs, by the appearance of new islands and mountains, by commotions propagated with the rapidity of an electric shock, finally by those subterranean thunders*, which are heard during whole Those which alarmed the inhabitants of the town of Guanaxuato, in Mexico, lasted from the 9th of January till the 12th of February, 1784. This phenomenon, almost without example among those accurately observed, will be described in the sequel of this Narrative. It is sufficient here to observe, that the town is situate forty leagues North of the volcano of Jorullo, and sixty leagues North-West of the volcano of Popocatepetl. In places nearer these two volcanoes, three leagues distant from Guanaxuato, the subterraneous thunders were not heard. The noise was circumscribed within a very narrow space, in the region of a primitive schist, which approaches a transition schist, containing the richest silver mines of the known world, and on which rest trap porphyries, slates, and diabasis (gruenstein). months, without shaking the earth, in regions far distant from active volcanoes. In proportion as equinoctial America shall increase in culture and population, and the system of volcanoes of the central table-land of Mexico, of the Caribbee islands, of Popayan, of Los Pastos, and Quito, are more attentively observed, the connection of eruptions and of earthquakes, which precede and sometimes accompany these eruptions, will be more generally recognized. The volcanoes we have just mentioned, particularly those of the Andes, which rise above the enormous height of two thousand five hundred toises, present great advantages for observation. The periods of their eruptions are singularly régular. They remain thirty or forty years without emitting scoriæ, ashes, or even vapours. In this interval, I could not perceive the smallest trace of smoke on the summit of Tunguragua or Cotopaxi. A gust of vapours, issuing from the crater of Mount Vesuvius, scarcely attracts the attention of the inhabitants of Naples, accustomed to the movements of that little volcano, which throws out slags sometimes during two or three years successively. It thence becomes difficult to judge, whether the emission of slags have been more frequent at the time when an earthquake has been felt in the Apennines. On the ridge of the Cordilleras every thing assumes a more decided character. An eruption of ashes, which lasts only a few minutes, is often followed by a calm of ten years. In such circumstances, it is easy to mark the periods, and recognize the coincidence of phenomena. Admitting what we cannot doubt, that the destruction of Cumana in 1797, and that of Caraccas in 1812, indicate the influence of the volcanoes of the Caribbee islands* on the commotions felt on the coasts of Terra Firma, it will be advantageous, before we close this The following is the series of the phenomena: 27th of September, 1796. Eruption in the West India islands. Volcano of Guadaloupe. November, 1796. The volcano of Pasto begins to emit smoke. 14th of December, 1796. 4th of February, 1797. 30th of January, 1811. the Azores. It increases 1811, Destruction of Cumana, Destruction of Riobamba." Appearance of Sabrina island, in particularly on the 15th of June, May, 1811. Beginning of the earthquakes in the island St. Vincent, which lasted till May, 1812. 16th of December, 1811. Beginning of the commotions in the Valley of the Missisippi and the Ohio, which lasted till 1813. December, 1811. Earthquake at Caraccas. 26th of March, 1811. Destruction of Caraccas. Earthquakes which continued till 1813. 30th of April, 1811. Eruption of the volcano in St. Vincent's; and the same day subterranean noises at Caraccas, and on the banks of the Apura. chapter, to take a rapid view of this Mediterranean Archipelago. The volcanic islands form one fifth of that great arch extending from the coast of Paria to the peninsula of Florida. Running from South to North, they close this interior sea on the eastern side, while the Greater West India islands appear like the remains of a group of primitive mountains, the summit of which seems to have been between Cape Abacou, Point Morant, and the Copper Mountains, at that spot, where the islands of St. Domingo, Cuba, and Jamaica, are nearest to each other. Considering the basin of the Atlantic as an immense valley*, which separates the two continents, and where, from 20° South to 30° North, the saliant angles (Brazil and *See my first geological sketch of South America, pubished by Mr. de la Metherie in the Journal de Physique, vol. liii, p. 33. The coasts of the ancient continent, between 5° and 10° North, have the same direction (from S. E. to N. W.) as the coasts of America between 8° South and 10° North. The direction of the coast is, on the contrary, from S. W. to N. E. in America, between 30, and 72°; and in the ancient continent between 25° and 70°. The valley is narrowest (300 leagues) between Cape St. Roch and Sierra Leone. Proceeding toward the North along the coasts of the New Continent, from it's pyramidal extremity, or the Straits of Magellan, we imagine we recognise the effects of a repulsion directed first toward the North-East, then toward the North-West, and finally again to the North-East. Senegambia) correspond to the entering angles (the gulf of Guinea and the sea of the West Indies), we are led to think, that the latter sea owes it's formation to the action of currents, flowing, like the current of rotation now existing, from East to West; and which have given the southern coast of Porto-Rico, St. Domingo, and the Island of Cuba *, so uniform a configuration. This supposition, not improbable, of an oceanic irruption, has been the source of two other hypotheses on the origin of the Smaller West India islands. Some geologists admit, that the uninterrupted chain of islands from Trinidad to Florida exhibits the remains of an ancient chain of mountains. They join the chain sometimes to the granite of French Guiana, sometimes to the calareous mountains of Pari. Others, struck with the difference of geognostical constitution between the primitive mountains of the Greater West India islands and the volcanic cones of the Less, consider these last as having risen from the bottom of the sea. If we recollect, that volcanic swellings, when they take place through elongated crevices, affect most commonly a straight direction, we shall find it difficult to judge from the disposition of the craters alone, whether the volcanoes • Between Cape Mayzi and Cape Cruz. |