Cordillera, a Spanish word meaning a mountain chain or ridge. It is commonly applied to the whole or a portion of the chain of the Andes, as la Cordillera de los Andes; la Cordillera de la Costa, the chain which runs near the Pacific coast; and la Cordillera Real, the northern prolongation in Venezuela and Colombia of the main interior chain. Some authorities consider the Cordilleras of Central America and those extending northward near the Pacific to the frigid zone as the continuation of the Andes, forming with them one range from the Antarctic to the Arctic ocean, and that hence they should be described under one common name. But the break at the isthmus of Panama, the only one in the chain between this point and the straits of Magellan, the diverging course of the ranges of the Andes as they approach the northern limits of South America, and the fact that the comparatively low elevation of the isthmus can at the most be called the continuation of the inferior Cordillera of the coast, taking on the other side of the break an entirely new course, as it sweeps round to N. W. - these lead others to the conclusion that the mountain ranges of North and South America are too distinct from each other to be classed as one range, notwithstanding they are connected by the continuation throughout their extent of the same great geological formations.

The South American Cordilleras have been treated under the title Andes; the ranges through Central America and Mexico may be described under the present head; while to their extension further north the name Rocky Mountains is given. - Upon the isthmus the Cordilleras present the lowest and narrowest barrier between the two oceans. The distance across varies from 30 to 70 m. The railroad constructed from Aspinwall on the Atlantic side to Panama on the Pacific coast traverses the isthmus in a length of 49 m., ascending to the summit level only 300 ft. It is said that the summit level between Port Escoces on the Atlantic and the mouth of the Savanna in the harbor of Darien is only 150 ft. above the sea, and this point is suggested as the most favorable for a ship canal between the two oceans. Yet the mountains, as seen from the sea, present the appearance of continuous ranges of great height, the overlapping of the ridges concealing the gaps, the valleys and low lands, and the thickly wooded plains that lie between the mountains.

The unhealthiness of this portion, the incessant rains that fall during a considerable part of the year, the almost impenetrable nature of its forests, and the inhospitable disposition of the Indians that occupy the territory, have prevented its resources from being developed. These ridges present steep slopes toward the Pacific; on the Atlantic side they fall away more gently. The San Juan river finds its way through them from Lake Nicaragua to the Atlantic, the main range, called the Alto Grande, continuing to the N. E. of this lake and of the adjacent smaller lake, Managua. On the other side a straight and narrow mountainous belt separates these lakes from the Pacific, which belt is so unbroken that, though the waters of the lakes and the ocean approach within 12 m. of each other, and a stage road passes across from Rivas to San Juan del Sur, yet no favorable route appears to exist for the construction of a ship canal, even if the rapids of the San Juan in its passage through the Cordilleras were so improved as to form a part of the interoceanic communication.' Along this western range occur several volcanoes and many extinct craters and beds of lava, though the real volcanic belt lies a little further east, passing through the western portion of the two lakes.

The central basin between the two outer mountain ranges, including the two lakes, and extending about 300 m. in length by about 150 in width, comprises the fine state of Nicaragua, a country presenting the greatest diversity of beautiful scenery. The rugged mountains on each side are the frames in which are included the broad fertile plains and the large lakes, one of which extends in a parallel direction with the mountains a distance of about 100 m. From its surface and on its shore huge volcanoes rise abruptly to the height of several thousand feet; others appear ranged along the same line, disturbing the smooth contour of the vast plains, above which they stand dark and gloomy, their sides rent with the deep volcanic fissures and black with their covering of ancient lavas. The shores of the lakes are covered with the dense vegetation of the tropics, while the broad slopes of the Alto Grande overlooking them are the open grazing lands for countless herds of cattle. Beyond these, along the summits of the great range, and upon the sources of the streams which flow into the Atlantic, is the mineral region of Chontales, Matagalpa, and Segovia, extending further northward into Honduras. The geological formations of the western portion of the basin appear to be almost wholly of a volcanic character, as basaltic rocks and lava, with limestone and a calcareous breccia formed in great part of volcanic products.

The volcanoes still emit smoke and sometimes flame from their summits, but streams of lava are rarely known to flow from them. Some of the larger, as that of Momobacho (about 5,000 ft. high) on Lake Nicaragua, a few miles S. of the city of Granada, are regarded as extinct. The volcanic cone of Ometepec, upon an island in the same lake, is very regularly shaped, and, like the neighboring summit of Madeira, rises to a greater height than Momobacho. The volcanoes El Viejo and Momotombo, N. W. of Lake Managua, are about 6,000 ft. high. The climate of this portion of the Cordilleras is salubrious and of moderate temperature, cooled by the trade winds after these have shed a considerable portion of the moisture they come charged with from the Atlantic upon the easternmost ridges of the range. The rains are therefore not excessive even during the rainy season, which extends from May to November. The thermometer during this season rarely sinks by night so low as 70° upon the plains, or rises in the day to 90°. In the dry season the temperature is somewhat lower, and the nights are cool, especially upon the mountains. - Through Honduras, San Salvador, and Guatemala the Cordilleras continue with little variation of character.

On the east they send out spurs toward the Atlantic, and the inferior volcanic range still skirts the Pacific. Five volcanoes are enumerated in San Salvador, the most active of which is Yzalco, and the two highest, San Vicente and San Salvador, are each estimated to rise to an elevation of about 7,500 ft. In Guatemala six volcanoes are in activity, viz.: Pacaya, Fuego, Agua (which pours forth torrents of water), estimated to be about 14,000 ft. high, Atitlan, 12,500 ft., Sapotitlan and Amilpas, 13,000 ft. Earthquakes are frequent throughout this region. Upon the main range of the mountains, in the department of Tegucigalpa in Honduras, at the source of the Patuca or Patook, which flows into the Atlantic, it is stated that 40 silver mines are found within a circuit of 30 miles radius; but from want of enterprise in the inhabitants they are worked to little advantage. Near the Pacific coast copper ores are found abundantly, but they too are neglected. They are also met with in the Le-paguare valley in the department of Olancho, and were formerly worked to supply the mint at Tegucigalpa, the ores being carried eight days' journey upon the backs of mules.

These regions produce in great abundance valuable mahogany, rosewood, red cedar, boxwood, India rubber, vanilla, cochineal, sarsaparilla, etc, large quantities of most of which are floated down the Patuca to the Atlantic coast. The temperature of the interior region is never excessive; the thermometer during the dry season from November to February seldom rises above -80° F. at noon, or falls below 55° in the morning. During the summer wet months at Jutecalpa, considerably to the eastward of the main range and below its summits, the nights are said to be always cool, and the extreme temperature of the day is below 95°. - Passing from Guatemala into Mexico, the mountain ranges diminish in height. At the isthmus of Tehuantepec one may pass from ocean to ocean over a summit not more than 700 ft. high. The mountains thence to the northern limits of the state spread out in a vast plateau, the height of which along its middle portion is from 6,000 to 8,000 ft. above the sea, and its greatest width near the latitude of the city of Mexico is about 3G0 m. It extends N. W. at this elevation full 600 m., presenting a smooth surface, mostly unsheltered by the growth of forest trees, though the soil is naturally fertile.

Still further N. for 900 m. the plateau is traced at an elevation of from 2,000 to 3,000 ft. On either side one descends from this cool elevated region by successive steps to lower plateaus, each descent bringing the traveller into a region of warmer temperature and of more tropical productions. From the tierra fria, or cold region, the first descent is to the tierra templada, or temperate tract; the next to the tierra caliente, the low lands along the coasts, hot and unhealthy. So steep are the walls of these plateaus, that for a distance of 500 m. only two roads passable by carriages lead from the Atlantic coast into the interior - one passing from Vera Cruz through Jalapa, and the other by Saltillo west of Monterey. On the western side the descent is hardly less precipitous, and to the south the great plateau ends abruptly near the shores of the Pacific. The climate of the plateau, though called cold, is said not to differ in its mean temperature (which is about 62° F.) from that of the central parts of Italy. There are some still more elevated tracts, as the valley of Toluca, about 8,500 ft. above the sea, where the thermometer during a great part of the day rarely rises beyond 45° F. The volcanic mountains, which are still met with along the chain as far as lat. 24° N., rise from the great plateau in stupendous masses, and penetrate with their lofty peaks the limits of perpetual snow.

Their range is not, as in the more southern states, near to and parallel with the Pacific coast, but a line of them appears to cross that of the great mountain chain in an E. and W. direction, passing about 16 m. S. of the city of Mexico. The most western of them, Colima, stands alone upon the plain of the same name, situated between the plateau and the Pacific. Its height is about 12,-000 ft. Smoke and ashes are frequently thrown from its crater, and an eruption began in 1869 in which vast quantities of pumice stone were ejected. Jorullo, upon the western slope of the plateau, 70 m. from the Pacific, is described by Humboldt as suddenly appearing above the surface in the night of Sept. 28 and 29, 1759, after a succession of earthquakes, accompanied by constant subterranean noises, which had continued for about three months. A tract covering several square miles rose above the plain to the height of 524 ft. Flames burst forth from all parts of this area, and burning rocks were thrown with vast clouds of ashes into the air, the softened surface of the earth rising and falling like the waves of the sea. Rivers of water flowing into the chasms caused eruptions of mud- to issue from thousands of little cones that appeared upon the surface.

In the midst six mountain masses were suddenly formed along a chasm ranging from N. N. E. to S. S. W. The principal one of them is the great volcano Of Jorullo. Its height above the sea is 4,265 ft.; that of the plain upon which it stands is 2,890 ft. Its great eruptions continued till the month of February, 1760; subsequently they became less frequent. A wall of basalt forms the boundary of the upheaved tract, which in most places, especially on the western side, is too steep to be ascended. The celebrated valley of Mexico, nearly 7,500 ft. above the sea, and covering an area of 18 leagues in length by 12 1/2 in breadth, is encircled by groups of mountains, among which are the famous volcanic peaks of Popocatepetl, Iztaccihuatl, and Toluca. The first rises to the height of 17,720 ft. above the sea, and 500 ft. above the termination of vegetation. Its crater is 3 m. in circumference and 1,000 ft. deep, and is in continual eruption. The second is an extinct volcano 15,705 ft. high. A chain of small volcanoes connects these with each other, and with the other volcanoes further east.

The Cofre de Perote lies between Popocatepetl and the fiery Orizaba, or Citlaltepetl, "the mountain of the star," so named for the fires that ever issue from its snow-enveloped summit, dispelling as by the light of a brilliant constellation the darkness of the night through the surrounding country. Orizaba, as measured by Ferrer in 1796, is 17,879 ft. high; but later calculations by Humboldt and others reduce these figures somewhat. It is generally thought that Popocatepetl is the higher of the two, and consequently the highest peak in Mexico. Below the plateau, in the region of low hills near the gulf of Mexico, is Tuxtla, the last of the volcanoes upon this line, a few miles west of Vera Cruz. It was in operation in 1793, when the ashes thrown from its crater were carried as far as Perote, a distance of 57 leagues. The great Mexican plateau, though a considerable portion of it is as level apparently as the ocean itself, is cleft by fissures called barancas, two or three miles in length, and often 1,000 ft. deep.

A brook or small river flows at the bottom, the banks of which are the precipitous and rugged walls of the chasm.

Some mountain ranges besides those of the volcanoes rise above the plain, as one bordering it on the eastern side, and the Sierra Madre, which, commencing at lat. 21° N., and extending 60 m. farther north, separates it for this distance into two portions. Other ridges here unite with it, spreading out into the mountainous district of Zacatecas, celebrated for its rich silver mines. Beyond this the Sierra Madre forms a belt of full 100 m. in breadth of parallel ridges and valleys extending to New Mexico, where it unites in lat. 33° N. with the southern portion of the Rocky mountains. Between the Rio Colorado and the Rio Grande del Norte, some of the summits of the Sierra Madre exceed 10,000 ft. in height above the sea, and are continually covered with snow. The geological structure of the Cordillera of Mexico is that of granitic and volcanic rocks, together with the micaceous, talcose, and clay slates, which form a considerable portion of the range, especially in the mining districts. So many of the rich silver mines of Mexico are found in porphyry, that its presence is regarded as particularly favorable for the existence of this metal.

It is also found, however, in the metamorphic limestones, and in those called by Humboldt the Alpine and the Jura. In no part of the range of the Cordilleras in North and South America has the production of this metal been so great as in Mexico. It was estimated by Humboldt to be ten times as great as that furnished by all Europe, and two thirds of the whole production of the globe. The vegetation of the elevated country varies with its height. On the high plains the forests destroyed by the early Spanish settlers have never been renewed, though there are still to be seen fine open groves of gigantic oaks and pines, clear of undergrowth. The plains as seen about the city of Mexico are not always fertile, but are covered in many places with saline incrustations.