These remarks have not escaped the learned author of the Classification Mineralogique des Roches; they must have presented themselves to an experienced geognost, who has so successfully investigated the superposition of the deposits of which he has treated. "We must not confound," says M. Brongniart, in his late Memoir on the position of the Ophiolites, "the relative positions, the orders of superposition of the deposites and of the rocks which compose them, with purely mineralogical descriptions. The neglect of making the proper distinction in this case, would necessarily be productive of confusion in the science, and would retard its progress." The arrangement which we give at the end of this article, is by no means what is called a classification of rocks; there will not even be found united, under the title of particular sections (as in the old geognostical method of Werner, or in the excellent Traité de Geognosie of M. D'Aubuisson), all the primitive formations of granite, nor all the secondary formations of sandstone and limestone. It has been attempted, on the contrary, to place each rock as it occurs in nature, according to the order of its superposition or of its respective age. The different formations of granite are separated by gneisses, mica-slates, black-limestones, and grey-wackes. In the transition rocks, we have separated the formations of porphyries and syenites of Mexico and Peru, which are anterior to the grey-wacke, and to the limestone with orthoceratites, from the much more recent formation of the zircon-porphyries and syenites of Scandinavia. In the secondary rocks, we have separated the oolitic sandstone of Nebra, which is posterior to the alpine limestone or zechstein, from the red-sandstone, which belongs to the same formation with the secondary porphyry and amygdaloid. According to the principle which we follow, the same names of rocks occur several times in the same table. Anthracitic mica-slate is separated, by a great number of older formations, from the mica-slate anterior to the primitive clay-slate.

Instead of a classification of granitic, schistose, calcareous and arenaceous rocks, it has been my object to present a sketch of the geognostical structure of the globe; a table in which the superimposed rocks succeed each other, from belaw upwards, as in those ideal sections which I designed in 1804, for the benefit of the Mexican School of Mines, and of which many copies have been distributed since my return to Europe. (Bosquejo de una Pasigrafia geognostica, con tablas que ensenan la estratificacion y el parallelismo de las rocas en ambos Continentes, para el uso del Real Seminario de Mineria de

Mexico). These Pasigraphic tables united to my own observations made in both Americas what had at that period been known with precision regarding the relative position of the primitive, intermediary and secondary rocks in the Old Continent. They presented, together with the type which might be considered as the most general, the secondary types, that is to say, the beds which I have named parallel. This same method has been followed in the work which I now publish. My parallel formations are geognostical equiva lents; they are rocks which represent each other. (See the Traité de Geologie de M. d'Aubuisson, vol. ii. p. 255). In England, and on the opposite Continent, there does not exist an identity of all the formations: there exist equivalents or parallel formations. That of our coal situated between the transition masses and the red-sandstone, the position of the rock-salt which occurs on the Continent in the alpine limestone, and the position of our oolites in the Nebra sandstone and Jura limestone, may guide the geognost in the approximation of remote formations. In England, we observe the coals placed upon transition formations; for example, upon the mountain-limestone of Derbyshire and of South Wales, and upon the transition sandstone, or old red-sandstone of Herefordshire. I have thought that I recognized in the magnesian-limestone the red marl, the lias and white oolites of Bath, the united formations of the alpine limestone, of the oolitic sandstone and Jura limestone. In comparing the formations of countries more or less distant from each other, those of England and of France, for instance, of Mexico and Hungary, of the secondary basin of Santa Fe de Bogota and of Thuringia, we must not think of opposing to each individual rock a parallel one; it must be recollected, that a single formation may represent several others. It is according to this principle that beds of clay, lying beneath the chalk, may, in France, be separated in the most distinct manner from the oolitic limestone beds: while in Switzerland, in Germany, and in South America, they have for equivalents beds of marls subordinate to the Jura limestone. The gypsums, which, in one district, are sometimes only intercalated beds in the alpine limestone or oolitic sandstone, in another district, assume all the appearance of independent formations, and occur interposed between the alpine limestone and the oolitic sandstone, between this sandstone and the muschelkalk. The learned Oxford Professor, Mr Buckland, whose extensive researches have been equally useful to the geognosts of England and of the Continent, has lately published a table

of parallel formations, or, as he calls them, equivalents of rocks, which only extends from the 44th to the 54th degree of north latitude, but which merits the greatest attention. (On the Structure of the Alps, and their relation with the rocks of England, 1821.)

As in the history of ancient nations, it is easier to verify the series of events in each country, than to determine their mutual coincidence; so also more accuracy can be attained in estimating the superposition of formations in isolated regions, than in determining the relative age or parallelism of formations which belong to different systems of rocks. Even in countries which are not widely separated, in France, in Switzerland, and in Germany, it is not easy to fix the relative antiquity of the muschelkalk, of the molasse of Argovie, and of the quadersandstein of the Hartz; because rocks of general occurrence are here most commonly wanting, which, according to the happy expression of M. de Grüner, serve as a geognostical horizon, and with which we might compare three formations in question. When rocks are not in immediate contact, we can only judge of their parallelism by the relations of age existing between them and other formations by which they are united.

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These inquiries of comparative geognosy, will long occupy the sagacity of observers; and it is not surprising that those who set out with the idea of retracing each formation in all the individuality of its relative position, interior structure, and subordinate beds, should finish with utterly denying all analogy of superposition. I had the advantage of visiting, previous to my journey to the Equator, a great part of Germany, of France, of Switzerland, of England, of Italy, of Poland, and of Spain. During these excursions, my attention was particularly directed to the relative position of formations, a phenomenon which I calculated upon discussing in a special work. On my arrival in South America, and while at first traversing in different directions the vast deposites which stretch from the maritime chain of Venezuela to the basin of the Amazon, I was singularly struck with the conformity of position which the two Continents present. (See my first sketch of a Geological Table of Equinoctial America, in the Journal de Phys., vol. liii. p. 38). Subsequent observations, which included the Cordilleras of Mexico, of New Grenada, of Quito, and of Peru, from the 21st degree of north latitude to the 12th degree of south latitude, have confirmed these first perceptions. But in speaking of analogies which are observed in the relative position of rocks, and of the unifor

mity of those laws which reveal to us the order of Nature, I might adduce a testimony otherwise of more weight than mine, that of the great geognost whose works have thrown the greatest light upon the structure of our globe. M. Leopold de Buch has pushed his researches from the Archipelago of the Canary Isles to beyond the Polar Circle to the 71st degree of latitude. He has dicovered new formations situated between others already known; and, in the primitive as in the transition deposites, in the secondary as well as in the volcanic, he has been struck with the great features by which the table of formations is characterized in the most distant regions.

(To be continued.)

ART. III.-Account of the Earthquake in Chili, in November, 1822, from observations made by several Englishmen residing in that country. Communicated by F. Place, Esq. [Jour. Roy. Inst.]

CHILI is a long narrow country, lying between the mountains of the Andes on the east, and the Pacific Ocean on the west. It extends from 20° 20′ to 43° 50′ south latitude, and from 68° 50′ to 74° 20′ west longitude from Greenwich, its length being about 1350 miles, and its average breadth about 130 miles.

While under the dominion of Spain, Chili was visited by very few Europeans. Its great fertility, its abundance of metals and minerals, its agreeable and healthy climate, have, since it has been declared independent, induced a considerable number of Englishmen, and a few other foreigners to become residents, and the number is continually increasing.

The country rises gradually but irregularly from the sea. coast to the mountains; it is exceedingly diversified, but the principal feature is its formation into valleys, surrounded by hills, many of them rising to a considerable elevation.

The whole country may be divided into two regions or climates, the one humid, the other dry, separated from each other by the river Maule, which in 35° 10′ falls into the Pacific Ocean.

South of the river Maule the climate is variable; rain falls at intervals during the whole year, and timber trees are in abundance. North of the river Maule the rains are periodical, and fall only during a particular time of the year. At Valparaiso, the principal seaport of Chili, and for about

forty miles to the northward, the rainy season commences in May and terminates in September. Further to the northward, the rainy season is of shorter duration, diminishing gradually, until at the northern extremity of the country, it totally ceases. To the southward of the Maule the time in which rain falls gradually increases, and, at the southern extremity of the country, there are but few intervals of dry weather.

Chili is never free from earthquakes; scarcely a week ever passes without one or more being felt, in some part of the country, but as the shocks seldom do any damage, the inhabitants pay but little regard to them.

It is now nearly a hundred years since the former great earthquake, and a persuasion seems to have prevailed among the people that no very considerable earthquake would happen oftener than once in two hundred years. Partial earthquakes, doing much damage, have always happened at intervals of a few years. The town of Coquimbo was nearly destroyed by an earthquake in 1820. The shock was local, and produced no alarm in other parts of the country.

On the fourth of November, 1822, the town of Copiapo, in S. Lat. 27° 10', was visited by a severe shock, which damaged many houses; this was followed, the next day, by a much more violent earthquake, which nearly destroyed the town, and did considerable injury to the town of Coquimbo, in S. Lat. 29° 50'.

The great earthquake on the night of the 19th of November, 1822, was felt over the whole surface of the country, from the mountains to the sea, and from one extremity to the other. Its force seems to have diminished in a pretty exact proportion to its distance from Valparaiso.

Its effects are thus described by an Englishman, residing at Concon, near the mouth of the river named in the maps "Rio Quillota." Concon is about fifteen miles N. N. E. of Valparaiso, as the crow flies.

"At half past ten, on the night of the 19th November, I felt the first oscillation. I was writing at the time; starting from my chair, I paused for an instant, expecting the shock would subside, as others had done; but the falling of glasses from the sideboard, the cracking of the timbers, and the rattling of the tiles from the roof, fully apprized the whole family of their danger, and all ran out of the house. The house was violently agitated, and was falling to pieces; but freed from the apprehension of being buried in the ruins, my attention was forcibly drawn to the phenomena, which I endeavoured to observe as accurately as possible. Scarcely,