Cotopaxi, a volcano in Ecuador, in the E. chain of the Andes, 34 m. S. S. E. of Quito, in lat. 0° 45' 11" S., lon. 78° 42' W. Its summit, according to Humboldt, is 18,862 ft. above the sea; but Dr. Reiss, who was the first to ascend it, in November, 1872, states that the barometer gave a height of 19,660 ft., while bis trigonometrical observations, from different bases, gave to the northern peak an elevation of 19,-496, and to the southern peak 19,427 ft. The valley on the western side, which separates this from the next chain, lies itself at an elevation of about 9,000 ft., so that the great altitude of the mountain is lost in that of the group to which it belongs. The waters upon its S. and E. slopes find their way into the river Na-po, a tributary of the Amazon; while those on the N.W. side flow N.W. past Quito, and in the river Esmeraldas are discharged into the Pacific in the comparatively short course of about 200 m. Cotopaxi is remarkable as the highest active volcano in the world. It is distinguished also for its symmetrical figure, gradually sloping up from its immense base in the form of a cone, which below the apex is cut off to form a summit, in which is the crater.

This, as seen by Reiss, is of an elliptical form, the major axis lying N. and S.; he estimated the depth to be 1,500 ft., and there were no indications of a level bottom. In the sides are many large fumorolas, sending forth dense masses of vapor charged with gas, and having a temperature of 156°. Around the edge is seen a circular wall of rock, which, examined by a telescope, appears like an artificial parapet. The steepness of this wall, and the crevices through it, by which the heated vapors of the volcano escape, are supposed to prevent the snow from lying here, as it does below for a vertical descent of about 4,400 ft. Upon this belt none of the irregularities of structure of the mountain are perceived. All lies concealed beneath an unknown depth of snow, which undergoes no apparent change except along its lower margin. Below this succeeds another marked belt, distinguished by its barren aspect, clothed but with small shrubs and lichens; and this gradually gives place to the forest belt, which extends to the base of the mountain. Nowhere are these divisions so conspicuously marked as in the high mountains of this portion of the Andes. The snowy belt of Cotopaxi is an especial object of admiration.

Seen through the pure atmosphere in summer evenings, its color changes according as the rays of the setting sun are reflected from its surface; it appears at one time silvery white and dazzling, and again like a mass of burnished gold. The rocky portions present darker shades, often assuming violet and purple tints of wonderful beauty and magnificence. Sometimes, however, the cone appears black, owing to the snow being covered with ashes. Out of its summit arises a column of smoke, and occasionally discharges like those of bombs are heard, accompanied with emissions of fire, visible at night. The flow of lava is of rare occurrence, as in all the South American volcanoes. The first eruption on record occurred in the year 1533. On the S. side of Cotopaxi is a porphyritic peak known as the "Indian's Head," which tradition says was the original summit of the volcano, torn off Aug. 29, 1533, the day on which Atahuallpa was put to death by Pi-zarro. Dr. Reiss thinks that it forms no part of Cotopaxi, but belongs to a more ancient volcano. In 1698 the town of Tacunga, 8 leagues distant S. S. W., was destroyed by an eruption. In 1743 and 1744 flames were seen issuing through innumerable crevices around the crater, and rising from its summit to great heights in the air.

The snow on the evening of June 15 was melted, and torrents of water were poured down the sides of the mountain, devastating the country around. Rocks as large as the huts of the Indians are said to have been thrown as far as 9 or 10 m. from the mountain. La Condamine, who for several years previous had been in the vicinity, and in 1738 had made unsuccessful attempts to scale the peak, was a witness to some of these eruptions. The eruption of April, 1768, is reputed to have been the most terrible of all. Showers of ashes and clouds of smoke sent forth from the crater obscured the light of the sun, producing such darkness that the inhabitants of Tacunga and Hambato were obliged to grope their way with lanterns till 3 P. M. The ashes were carried through the air even to Guayaquil, 130 m. distant, and Po-payan. A deluge was produced in 1803. During this eruption Humboldt, who was at Guayaquil, heard day and night the explosions of the volcano, which resembled heavy discharges of artillery. From that time the volcano remained tranquil till 1851, when flames again appeared at its summit, dense clouds of smoke rolled forth from the crater, and small eruptions occurred on its eastern slope.

In 1855 a greater eruption took place on the W. side, in which lava and burning stones were ejected, and water was poured down the sides of the mountain. Reiss found this lava stream. It was still warm, having a temperature of from 68° to 90°, that of the surrounding air being 32°. Its greatest width was about 3,000 ft. and the estimated thickness 150 ft. No fissure or accumulation of scoriae indicated its source; but its point of departure is by his observations 18,700 ft. above the sea. In 1856 occurred another on the E. side.

Cotopaxi, viewed from Salto.

Cotopaxi, viewed from Salto.