No volcanoes are spoken of in it, but they may be there and have escaped the observation of civilized man. The volcanoes of Quito extend from 100 m. S. of the equator to 130 m. N. of it; and from their northern termination it is about six degrees further to the southern termination of the volcanoes of Central America. They are not only remarkable for the long line of country they spread over, but also for the great height of many of the peaks, and their extremely destructive character. The products of an eruption are usually water, mud, ashes, and fragments of pumice, trachyte, and porphyry. But the volcanoes of the Andes are singularly exempt from floods of lava. From high up the flanks of Antuco in Chili, the summit of which rises 16.000 feet above the sea, immense currents of lava flowed in 1828; but this is a rare occurrence, the matters usually ejected being vapors and scoria?. The outbursts of the volcanoes are closely connected with the frequent and disastrous earthquakes of this region. These commotions appear to extend under the whole range of the Andes, and even far out under the ocean.

So frequent are they that M. Boussingault is of opinion that a full register of them would show that they are incessant. - The geological structure of the Andes shows that the chain was slowly upheaved in mass from the sea, and has since undergone three subsidences. Indeed, there are evidences that the Andes are now subsiding again, for successive measurements indicate a lower elevation. (See '"American Journal of Science," October, 1871, p. 207.) In the pass of Uspa-llata, the two parallel ridges, based on the ancient porphyries, are capped, the range next the coast with black clay slates containing the grypheas, ammonites, and other fossil shells of Jurassic and cretaceous age, and altered by intrusion of the igneous rocks; while the eastern range is covered with still later formations, as sandstones and conglomerates made up of the fragments of the rocks of the western range, and bearing all the appearance of the tertiary strata found along the Pacific coast. These later formations also are intermingled with trap rocks and volcanic tuffs, and altered by contact with the granitic rocks, which since the deposition of the sedimentary rocks have intruded among the strata.

The metallic veins from the granite also penetrate them, and veins of gold have been worked in close proximity to fossil trunks of trees, found by Darwin standing imbedded in the stratified rocks. The Andes appear throughout their length to carry a similar geological structure, which is made manifest as well by a similarity of mineral productions as by the reports of those naturalists who have ascended the summits; granitic and porphyrinic rocks form the lower portion, and on these rest immense formations of mica slate, gneiss, and quartz rock. Upon the very summits are found the tertiary strata, which, like the same formation extending along the Pacific coast, are productive in beds of bituminous coal, and the variety called brown coal, at intervals from Patagonia to Panama. Beds of this coal are worked in Chili for the use of steamships; and in the mining region of Pasco in Peru, in the immediate vicinity of its celebrated silver mines, and at an elevation of over 14,000 feet, coal probably of the same age is found in abundance.

The quality of such coal is not likely to be as good as of the bituminous coals of the true coal formation, but our data are very imperfect on this point, as also whether the real carboniferous rocks are found at all in South America. The secondary rocks generally cover the granite in the mountains of Venezuela, but thin away toward the equator; and in the plains of the Rio Negro Humboldt noticed the bare granite in patches of 10,000 square yards forming the level surface. Mines of silver have frequently been alluded to in describing different localities along the Andes. Near the equator and N. of it they are not productive; but in Peru and Bolivia they are probably unsurpassed in richness by any mines of this metal in the world. The mines of cinnabar of Huanca Velica, in southern Peru, have in former times produced very large quantities of mercury, and the same ore is also found near Tarma in the valley of the Jauja river, and in the equatorial Andes, N. W. of Cuenca; platinum is met with in small grains in the alluvium near the Pacific coast of New Granada. Gold is found in the silver veins of Peru, and is worked in veins in Chili. In Bolivia it is washed from the deposits along the streams. Lead ores are common with those of silver, but are not regarded as of much value.

The copper mines of Chili are very productive in the rich oxides and carbonates of this metal. Many cargoes of these valuable ores are shipped every year to Swansea in Wales to mix with the lean ores of Cornwall; and our own copper-smelting establishments along the coast receive occasional supplies from the same source. The production of Chili, and of Peru also, in these ores might be largely increased, were there better facilities for getting the ores to the coast, or were there convenient supplies of fuel for converting them into products more economical for shipment. The nitrate of soda mines of Peru have already been noticed. The finest gem of the Andes is the emerald, the Tunca mines near Bogota furnishing nearly all in the market. - The name Andes, according to Gareilasso, is derived from Anti, the name of an ancient province E. of Cuzco. Others think it may have come from the aboriginal word anta, copper, this metal being so abun-dantly distributed through the mountains. Col. Tod, in his work on Rajasthan, notices that the northern Hindoos apply the name Andes to the Himalaya mountains.

But Humboldt says there are no means of interpreting it by connecting it with any signilication or idea; if such connection exist, it is buried in the obscurity of the past. - See " The Narrative of the Ten Years' Voyage of H. M. Ships Adventure and Beagle," by Captain King, Captain Fitzroy, and Charles Darwin (London, 1839); Darwin's "Geological Observations on South America" (London, 1846); "The U. S. Naval Astronomical Expedition to the Southern Hemisphere during the years 1849, '50, '51, 52," by Lieut. J. M. Gilliss and others (Philadelphia, 1856), especially vol. ii., on "The Andes - Minerals, Animals, Plants, and Fossils; " and "The Andes and the Amazon," by J. Orton (New York, 1870).