EARTHQUAKES OF THE NINETEENTH CENTURY.* Chili, 1835.-The latest earthquake by which the position of solid land is known to have been permanently altered, is that which occurred in South America, on the 20th of February, 1835. It was felt at all places between Copiapo and Chiloe, from north to south, and from Mendoza to Juan Fernandez, from east to west. "Vessels," says Mr. Caldcleugh, "navigating the Pacific, within 100 miles of the coast, experienced the shock with considerable force."t Conception, Talcahuano, Chillan, and other towns were thrown down. From the account of Captain Fitz Roy, R. N., who was then employed in surveying the coast, we learn that after the shock the sea retired in the bay of Conception, and the vessels grounded, even those which had been lying in seven fathoms water; all the shoals were visible, and soon afterwards a wave rushed in and then retreated, and was followed by two other waves. The vertical height of these waves does not appear to have been much greater than from sixteen to twenty feet, although they rose to much greater heights when they broke upon a sloping beach. According to Mr. Caldcleugh, a great number of the volcanos of the Chilian Andes were in a state of unusual activity, both during the shocks and for some time preceding and after the convulsion, and lava was seen to flow from the crater of Osorno. (See Map. Fig. 41, p. 376.) The island of Juan Fernandez, distant 360 miles from Chili, was violently shaken at the same time, and devastated by a great wave. Flames rose there from the sea about a mile from the shore, and illumined the whole island during the night, although it was afterwards ascertained that there was a depth of sixty-nine fathoms water in the spot where the flames had appeared.‡ "At Conception," says Captain Fitz Roy, "the earth opened and closed rapidly in numerous places. The direction of the cracks was not uniform, though generally from south-east to north-west. The earth was not quiet for three days after the great shock, and more than three hun Since the publication of the first edition of this work, numerous accounts of recent earthquakes have been published; but as they do not illustrate any new principle, I cannot insert them all, as they would enlarge too much the size of my work. Among the most violent may be mentioned those of March, 1829, near Alicant in Murcia-that of Sept. 1827, at Lahore, East Indies-of Jan. 15, 1832, which destroyed Foligno, in Italy,-June 24, 1830, in China, in Tayming, North of Houan-March 9, 1830, in the Caucasus at Kislier-April 1833, Manilla-1833, Isle of Lissa in Adriatic, and Opus. Von Hoff has published, from time to time, in Poggendorf's Annalen, lists of the earthquakes which have happened since 1821; and, by consulting these, the reader will perceive that every month is signalized by one or many convulsions in some part of the globe. Phil. Trans., 1836, p. 21. VOL. I.-2 X Ibid. p. 25. dred shocks were counted between the 20th of February and the 4th of March. The loose earth of the valley of the Biobio was everywhere parted from the solid rocks which bound the plain, there being an opening between them from an inch to a foot in width. "For some days after the 20th of February, the sea at Talcahuano,” says Captain Fitz Roy, "did not rise to the usual marks by four or five feet vertically. When walking on the shore, even at high water, beds of dead muscles, numerous chitons, and limpets, and withered sea-weed, still adhering, though lifeless, to the rocks on which they had lived, everywhere met the eye." But this difference in the relative level of the land and sea gradually diminished, till in the middle of April the water rose again to within two feet of the former high water mark. It might be supposed that these changes of level merely indicated a temporary disturbance in the set of the currents or in the height of the tides at Talcahuano; but on considering what occurred in the neighbouring island of Santa Maria, Captain Fitz Roy concluded that the land had been raised four of five feet in February, and that it had returned in April to within two or three feet of its former level. Santa Maria, the island just alluded to, is about seven miles long and two broad, and about twenty-five miles south-west of Conception. (See Map, Fig. 42.) The phenomena observed there are most important. "It appeared," says Captain Fitz Roy, who visited Santa Maria twice, the first time at the end of March, and afterwards in the beginning of April," that the southern extremity of the island had been raised eight feet, the middle nine, and the northern end upwards of ten feet, On steep rocks, where vertical measures could be correctly taken, beds of dead muscles were found ten feet above high water mark. One foot lower than the highest bed of muscles, a few limpets and chitons were seen adhering to the rock where they had grown. Two feet lower than the same, dead muscles, chitons, and limpets were abundant." "An extensive rocky flat lies around the northern parts of Santa Maria, Before the earthquake this flat was covered by the sea, some projecting rocks only showing themselves. Now, the whole flat is exposed, and square acres of it are covered with dead shell-fish, the stench arising from which is abominable. By this elevation of the land the southern port of Santa Maria has been almost destroyed-little shelter remaining there, and very bad landing." The surrounding sea is also stated to have become shallower in exactly the same proportion as the land had risen; the soundings having diminished a fathom and a-half everywhere around the island. At Tubal, also, to the south-east of Santa Maria, the land was raised six feet, at Mocha two feet, but no elevation could be ascertained at Valdivia, northward of Conception. Ischia, 1828.-On the 2d of February the whole island of Ischia was shaken by an earthquake, and in the October following I found all the houses in Casamicciol still without their roofs. On the sides of a ravine between that town and Forio, I saw masses of greenish tuff, which had been thrown down. The hot-spring of Rita, which was nearest the centre of the movement, was ascertained by M. Covelli to have increased in temperature, showing, as he observes, that the explosion took place below the reservoirs which heat the thermal waters.* Bogota, 1827.-On the 16th of November, 1827, the plain of Bogota was convulsed by an earthquake, and a great number of towns were thrown down. Torrents of rain swelled the Magdalena, sweeping along vast. quantities of mud and other substances, which emitted a sulphureous vapour and destroyed the fish. Popayan, which is distant two hundred geographical miles S. S. W. of Bogota, suffered greatly. Wide crevices appeared in the road of Guanacas, leaving no doubt that the whole of the Cordilleras sustained a powerful shock. Other fissures opened near Costa, in the plains of Bogota, into which the river Tunza immediately began to flow. It is worthy of remark, that in all such cases the ancient gravel bed of a river is deserted, and a new one formed at a lower level; so that a want of relation in the position of alluvial beds to the existing water-courses may be no test of the high antiquity of such deposits, at least in countries habitually convulsed by earthquakes. Extraordinary * Biblioth. Univ., Oct. 1828, p. 157.; and Férussac, Bulletin, &c., tome xi. p. 227. + Phil. Mag., July, 1828, p. 37. rains accompanied the shocks before mentioned; and two volcanos are said to have been in eruption in the mountain-chain nearest to Bogota. Chili, 1822.-On the 19th of November, 1822, the coast of Chili was visited by a most destructive earthquake. The shock was felt simultaneously throughout a space of 1200 miles from north to south. St. Jago, Valparaiso, and some other places, were greatly injured. When the district round Valparaiso was examined on the morning after the shock, it was found that the whole line of coast, for the distance of above one hundred miles, was raised above its former level.* At Valparaiso the elevation was three feet, and at Quintero about four feet. Part of the bed of the sea, says Mrs. Graham, remained bare and dry at high water, "with beds of oysters, muscles, and other shells, adhering to the rocks on which they grew, the fish being all dead, and exhaling most offensive effluvia."t An old wreck of a ship, which before could not be approached, became accessible from the land, although its distance from the original sea-shore had not altered. It was observed, that the water-course of a mill, at the distance of about a mile from the sea, gained a fall of fourteen inches, in little more than one hundred yards; and from this fact it is inferred that the rise in some parts of the inland country was far more considerable than on the borders of the ocean. Part of the coast thus elevated consisted of granite, in which parallel fissures were caused, some of which were traced for a mile and a-half inland. Cones of earth, about four feet high, were thrown up in several districts, by the forcing up of water mixed with sand through funnel-shaped hollows,-a phenomenon very common in Calabria, and the explanation of which will hereafter be considered. Those houses in Chili of which the foundations were on rock were less damaged than such as were built on alluvial soil. Mr. Cruckshanks, an English botanist, who resided in the country during the earthquake, has informed me that some rocks of greenstone at Quintero, a few hundred yards from the beach, which had always been under water till the shock of 1822, have since been uncovered when the tide is at half-ebb; and he states that, after the earthquake, it was the general belief of the fishermen and inhabitants of the Chilian coast, not that the land had risen, but that the ocean had permanently retreated. Dr. Meyen, a Prussian traveller, who visited Valparaiso in 1831, says that on examining the rocks both north and south of the town, nine years after the event, he found in corroboration of Mrs. Graham's account, that remains of animals and sea-weed, the Lessonia of Bory de St. Vincent, which has a firm ligneous stem, still adhered to those rocks which in * See Geol. Trans., vol. i., second series; and also Journ. of Sci., 1824, vol. xvii. p. 40. t Geol. Trans., vol. i., second series, p. 415. § Journ. of Sci., vol. xvii. p. 42. + Ibid. * 1822 had been elevated above high-water mark. According to the same author, the whole coast of central Chili was raised about four feet, and banks of marine shells were laid dry on many parts of the coast. He observed similar banks, elevated at unknown periods, in several places, especially at Copiapo, where the species all agree with those now living in the ocean. Mr. Freyer also, who resided some years in South America, has confirmed these statements;t but Mr. Cuming, a gentleman well known by his numerous discoveries in conchology, and who resided at Valparaiso during and after the earthquake, could detect no proofs of the rise of the land, nor any signs of a change of level. On the contrary, he remarked, that the water at spring-tides rose after the earthquake to the same point, on a wall near his house, which it had reached before the shocks. The opinions of this gentleman well deserve attention from those who may have opportunities of minutely investigating the Chilian coast; but after considering his objections to Mrs. Graham's account, even before the late convulsion, I felt satisfied with the proofs of elevation in 1822. Had I still cherished any scepticism, it would have been removed by the coincidence of the facts related by Captain Fitz Roy; a shaving occurred in 1835, thirteen years afterwards, in another part of the same country.‡ Extent of country elevated.—The area over which this permanent alteration of level is conjectured to have extended, in 1822, is 100,000 square miles. The whole country, from the foot of the Andes to a great distance under the sea, is supposed to have been raised, the greatest rise being at the distance of about two miles from the shore. "The rise upon the coast was from two to four feet:-at the distance of a mile inland it must have been from five to six, or seven feet." The soundings in the harbour of Valparaiso have been materially changed by this shock, and the bottom has become shallower. The shocks continued up to the end of September, 1823; even then, forty-eight hours seldom passed without one, and sometimes two or three were felt during twenty-four hours. Mrs. Graham observed, after the earthquake of 1822, that, besides the beach newly raised above high-water mark, there were several older elevated lines of beach one above the other, consisting of shingle mixed with shells, extending in a parallel direction to the shore, to the height of fifty feet above the sea." a.¶ In order to give some idea of the enormous amount of change which this single convulsion may have occasioned, let us assume that the extent of country moved was correctly estimated at 100,000 square miles,-an 33. Reise um die erde; and see Dr. Meyen's letter cited Foreign Quart. Rev. No. p. 13., 1836. Geol. Soc. Proceedings, No. 40. p. 179., Feb. 1835. Cuming, Geol. Proceedings, No. 42. p. 213. § Journ. of Sci., vol. xvii. Geol. Trans., vol. i., second series, p. 415. || Ibid., pp. 40. 45. |