| OCR Text |
Show OF VOLCANOS. 381 have probably been raised from a fissure of 420 English geographical miles long, traversing the Continent from the Pacific to the Atlantic Ocean. These assemblages of volcanos, whether in rounded groups or in double lines, show in the most conclusive manner that the volcanic agencies do not depend on small or restricted causes, in their proximity to the surface of the earth, but that they are great phenomena of deep-seated origin. The whole of the eastern part of the American Continent, which is poor in metals, is, in its present state, without fire-emitting mountains, without masses of trachyte, and perhaps even without basalt containing olivine. All the American volcanos are on the side of the Continent which is opposite to Asia, in the chain of the Andes, which runs nearly in the direction of a meridian, and extends over a length of 7200 geographical miles. The whole plateau or highland of Quito, of which Pichincha, Cotopaxi, and Tunguragua form the summits, is to be viewed as a single volcanic furnace. The subterranean fire breaks forth sometimes through one and sometimes through another of these openings, which it has been customary to regard as separate and distinct volcanos. The progressive march of the subterranean fire has been here directed for three centuries from north to south. Even the earthquakes which occasion such dreadful ravages in this part of the world afford remarkable proofs of the existence of subterranean communications, not only between countries where there are no volcanos (a fact which had long been known), but also between fireemitting openings situated at great distances asunder. Thus in 1797 the volcano of Pasto, east of the Guaytara River, emitted uninterruptedly for three months a lofty column of smoke, which column disappeared at the instant when, at a distance of 240 geographical miles, the great earthquake of Riobamba and the immense eruption of mud called "Moya" took place, causing the death of between thirty and forty thousand persons. The sudden appearance of the Island of Sabrina near the Azores, on the 30th of January, 1811, was the precursor of the terrible earthquake movements which, much farther to the west, shook almost incessantly, from the month of May, 1811, to June, 1813, |
