[58] This lake is the largest fresh-water accumulation in South America. It has diminished within the historic period. Its surface is 12,795 feet above the Pacific, or higher than the highest peaks of the Pyrenees.
[59] This is the loftiest summit of the Andes in the northern hemisphere, being 18,200 feet. It is also remarkable for being situated farther from the sea (120 miles) than any other active volcano.
[60] "As a general rule, whenever the mass of mountains rises much above the limit of perpetual snow, the primitive rocks disappear, and the summits are trachyte or trappean porphyry."—Humboldt. In general, "the great Cordilleras are formed of innumerable varieties of granites, gneiss, schists, hornblende, chloritic slates, porphyries, etc., and these rocks alternate with each other in meridional bands, which in the ridges frequently present the appearance of a radiated or fan-shaped structure, and under the plains are more or less vertical."—Evan Hopkins, F.G.S.
[61] Von Tschudi makes the incorrect statement that "throughout the whole extent of South America there is not a single instance of the Western Cordillera being intersected by a river." Witness the Esmeraldas.
[62] It is a singular fact that true trachyte, pumice, and obsidian are wanting in the volcanic Galápagos Islands, only 700 miles west of Pichincha.
[63] As many of the crystals are partly fused, or have round angles, the porphyries were probably formed by the melting of a crystalline rock, the base becoming fused into a homogeneous material, while the less fusible crystals remain imbedded.—Dr. Hunt.
[64] In the Galápagos volcanoes the south wall is lowest, while the craters in Mexico and Sandwich Islands are lowest on the northeast.
[65] The altitudes of the most important Ecuadorian volcanoes are:
| Western Chain. | Eastern Chain. |
| Chimborazo, 21,420 feet (Humboldt). | Cayambi, 19,648 feet (Humboldt); 19,358 (Wisse). |
| Caraguairazo, 19,183 feet (Humboldt).
It is variously estimated from 15,673 feet to 19,720 feet; 18,000 feet is not far from the truth. | Antisana, 19,148 feet (Humboldt); 19,279 (Wisse). |
| Cotopaxi, 18,880 feet (Humboldt); 18,862 (Wisse). | |
| Iliniza, 17,370 feet (Wisse); 16,300 (Hall). | Altar, 17,400 feet. |
| Cotocachí, 16,440 feet (Humboldt); 16,409 (Wisse). | Sangai, 17,120 feet (Wisse). |
| Pichincha, 15,922 feet (Humboldt); 15,827 (Orton). | Tunguragua, 16,579 feet (Humboldt). |
| Sincholagua, 16,434 feet (Humboldt). |
[66] The snow limit at the equator is 15,800 feet. No living creature, save the condor, passes this limit; naked rocks, fogs, and eternal snows mark the reign of uninterrupted solitude. The following is the approximate limit of perpetual snow in different latitudes: