VOLCANO. 



nd the 



ufually adds to the height and bulk of a volcano 

 matter difcharged by it for many ages would be fufficient to 

 form three fuch mountains as the fimple cone or mountam ot 

 the exifting volcano. r i • i. 



We have hitherto confined our account of volcanic phe- 

 nomena to thofe circumftances which accompany the erup- 

 tion in its immediate vicinity ; but in order to form any ra- 

 tional or probable conjedure refpeding the feat and origin 

 of volcanic fires, we mult take a more enlarged view of the 

 fubjed, and contemplate volcanic fires in conneaion with 

 each other, or in their effcfts on remote parts of the globe. 

 Volcanoes and earthquakes are regarded as diftinft pheno- 

 mena, but they are only different cffcfts of the fame caufe. 

 Volcanoes are the vents through which is difcharged the 

 elaftic vapour, and other materials, that, in a confined ftate, 

 are the principal caufes of earthquakes. Whenever thefe 

 vents are by any means choaked up for a long time, violent 

 commotions of the earth may be expeded, until the former 

 vents are re-opened, or new paffages made for the confined 

 materials to efcape. This view of the fubjed may he illuf- 

 trated by the following fafts, which prove the immediate 

 conneftion of earthquakes with volcanic fires. 



The great earthquakes which have (haken Sicily and Ca- 

 labria, have generally been accompanied with volcanic erup- 

 tions from Etna or the Lipari ifles. In the year 1169, 

 every houfe in Catania was thrown down by a violent earth- 

 quake, which occurred at the fame time with a great eruption 

 of Etna. 



The earthquakes of 1634 and 1635, which nearly de- 

 ftroyed Mefiina, accompanied the memorable eruption from 

 the fame mountam, in which part of the volcanic cone fell 

 down. The lava formed a torrent eighteen miles long, two 

 miles broad, and twenty-four feet high. Immediately pre- 

 ceding the earthquake which deftroyed Euphemia in 1633, 

 Kircher, who was an eye-witnefs, fays that Stromboli threw 

 out an immenfe quantity of flames, accompanied with a noife 

 which could be dlftindly heard at the diftance of fixty miles. 

 The common eruptions from this volcano are comparatively 

 feeble. 



Near the time of the great earthquakes which deftroyed 

 Lifbon in 1755 and 1761, Europe, Africa, and America were 

 repeatedly agitated by fubterranean commotions, accounts of 



which may be feen by referring to the journals of that period. 

 A few hours after the great fhock of the former earthquake, 

 the waters of Switzerland, Northern Europe, Canada, and 

 the Weft India iflands, were violently agitated, and fire was 

 feen to rife from the midft of the Atlantic ocean. Thefe 

 efforts, nearly fimultaneous, prove that the fource of the 

 commotion was feated deep within the globe. 



The earthquakes of Cumana, in New Andalufia, are con- 

 neded, fays Humboldt, with thofe of the Weft India 

 iflands ; and it has even been fuppofed that they have fome 

 connedion with the diftant volcanic phenomena of the 

 Andes. On the 4th of November, 1797, the province of 

 Quito fuffered fuch a deftrudive commotion, that even in 

 that thinly inhabited country, forty thoufand of the natives 

 perifhed, buried under the ruins of their houfes, fwallowed 

 up in the fiflufes, or drowned in lakes that were fuddenly 

 formed. At the fame period, the inhabitants of the Eaftern 

 Antilles were alarmed by ftiocks which continued eight 

 months, when the volcano of Guadaloupe threw out pumice- 

 ftones, alhes, and gufts of fulphureous vapours. This erup- 

 tion, during which long fubterranean nolfes were heard, 

 took place on the 27th of September, and was followed on 

 the [4th of December by the great earthquake at Cumana. 



The city of Caraccas was entirely deftroyed by an earth- 

 qmke on the 24th of March, 181 2 : violent ofcillations of 



the ground were felt for thirty-five days after, both in the 

 Weft India iflands, and on Terra Firma. At this time the 

 volcano in St. Vincent's, which had been dormant for near a 

 century, broke out with great fury, covering the neighbour- 

 ing iflands with its afties. On the night in which the cities 

 of Lima and Callao were deftroyed by an earthquake, four 

 new volcanoes broke out in the Andes. Humboldt alfo 

 ftates, that a column of denfe black fmoke, that had ilTued for 

 feveral months from a volcano on the (hore near Pafto, in 

 1797, dlfappeared at the very hour when the towns of 

 Rlobamba, Hambato, and Tacunga, fixty leagues to the 

 fouth, were overturned by a moft violent fhock. 



Numerous other inftances might be cited, were it necef- 

 fary, to prove the connedion exifting between the phe- 

 nomena of earthquakes and diftant volcanoes. The inha- 

 bitants in the vicinity of volcanoes are fo well aware of 

 this connedion, that at Meffina and Naples, and at the foot 

 of Cotopaxl and Tungurahua, earthquakes are only dreaded 

 when flames and vapours ceafe to ifl'ue from the craters ; 

 and what, fays Humboldt, is very remarkable, the ftiocks 

 appear to be ftronger, as the country is more diftant from 

 burning volcanoes. The globe, it may be faid, is agitated 

 with greater force, in proportion as the furface has a fmaller 

 number ef funnels communicating with the interior. 



The cataftrophe of Rlobamba, in Quito, before ftated, 

 has led feveral well-informed peribns to think that this un- 

 fortunate country would be lefs frequently defolated, were 

 the fubterranean fire to break the porphyritic dome of 

 Chimborazo, and this coloffal mountain were to become an 

 adive volcano. 



The connedion which diftant volcanoes have with each 

 other, and the vail extent to which the agitations of the 

 ground are felt during eruptions, offer fatisfadory proofs 

 that the fource of heat is not fituated in the middle of vol- 

 canic mountains, but is placed far below them ; or to fpeak 

 famiharly, a volcanic mountain is not the fire-place, but the 

 chimney-top. Our ideas of volcanic operations will be en- 

 larged by contemplating Ae immenfe craters of ancient vol- 

 canoes which are either become extlnd, or nearly fo. From 

 experiments made by Spallanzani to draw up the ftones 

 from the bottom of the fea between the iflands of Lipari, 

 Vulcano, and Salene, he learned that the ground was one 



continued mafs of volcanic fubftances, precifely of the fame 

 kind as thofe on the fhores of thefe iflands. Hence he in- 

 fers, that all the fubmarine ground between them has fuf- 

 fered the adion of fire, in the fame manner as that which 

 is expofed to view, and thefe three iflands are one continued 

 group of volcanized fubftances, and have originally been 

 formed by one central conflagration. That this eruption 

 has been fubfequently confined to three dlftind mouths, 

 which gave birth to the three iflands. Humboldt has 

 drawn nearly the fame inference refpeding the whole of the 

 mountainous part of the province of Quito, which, he fays, 

 may be confidered as one immenfe volcano, occupying feven 

 hundred fquare leagues of furface, and throwing out flames 

 by different cones, known under the denomination of dlftind 

 volcanoes, as Cotopaxl, Tungurahua, and Pichinca. In like 

 manner, he adds, the whole group of the Canary iflands is 

 placed as it were over one immenfe fubmarine volcano. 

 The fire makes its way fometimes through one, and fome- 

 times through another of thefe iflands in different parts. 

 Now if we confider this opinion as correft, how vaft and 

 deep muft be the volcanic abyfs to which the mountains of 

 Quito are only the different chimneys, placed over a thick 

 cruft of confolidated porphyritic lava. The volcanic cruft 

 which fupports the Canary ifles, muft cover an abyfs not 

 lefs in extent and depth than that of Quito. 



^ 5 The 



