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 extending eastward to the Brazilian frontier, but as Peru is in actual occupation of the region east of Huiririma-chico, on the Napo river, 3 degrees west of that frontier, those maps cannot be considered correct. The Trans-Andine territory occupied by Ecuador is a wedge-shaped area between the Coca and Napo, the provisional boundary line with Colombia, and a line running nearly west-south-west from Huiririma-chico (about lat. 2° 50′ S., long. 73° 20′ W.) to a point on the Santiago river in about lat. 4° 12′ S., long. 78° W., which forms the provisional boundary with Peru. The eastern part of this territory is also claimed by Peru, which would have the effect, if allowed, of restricting Ecuador to a comparatively small area covered by the Andes and western Cordillera and the narrow plain on the Pacific coast. From the Santiago river, a western affluent of the Marañon, the boundary line runs south-west and west across the Andes to the head waters of the Macara, down that stream to the Chira, or Achira, whose channel marks the frontier down to about 80° 17′ W., where a small stream (the Rio Alamo) enters from the north. The line then runs almost due north to the south shore of the Gulf of Guayaquil, following the western water parting of the lower Tumbez valley. A small district in the valley of the Chira is claimed by Peru. The northern boundary line is described elsewhere (see ). A small section of this line terminating on the Pacific coast is also in dispute, Ecuador claiming the main channel of the Mira as the dividing line, and Colombia claiming a small district south of that channel, the line running due west from the mouth of the most southern outlet of the Mira opening into Panguapi Bay, to a point of intersection with that river.

Physical Geography.—The surface of Ecuador may be divided into three distinct regions: the Cis-Andine lying between the Western Cordillera and the coast; the Inter-Andine, which includes the two great mountain chains crossing the republic with the elevated plateau lying between; and the Trans-Andine, lying east of the Andes in the great Amazon valley. The first part consists of an alluvial, low-lying plain formed in great part by the detritus brought down by the mountain streams. It is irregular in form and is broken by isolated elevations and spurs from the Cordillera. Large areas are still subject to annual inundations in the rainy season, and the lower river courses are bordered with swamps. This is the most fertile and productive part of Ecuador, especially on the higher lands near the Cordillera. The Trans-Andine region is similar to the neighbouring territories of the upper Amazon basin occupied by Colombia, Brazil and Peru—a great forest-covered plain descending gently toward the east, broken on its western margin by short spurs from the Andes enclosing highly fertile valleys, and by low, isolated ranges between the larger river courses, and traversed by large rivers flowing into the Napo and Marañon. This region has been only partially explored, and but little is known of the large areas lying between the navigable rivers.

The Inter-Andine or plateau region lies in and between the two great mountain chains which cross the greater part of the republic between and almost parallel with the 78th and 79th meridians. The eastern chain is known as the Andes of Ecuador, or the Cordillera Oriental, and the western as the Cordillera Occidental (Western Cordillera). Starting from the confused grouping on the southern frontier of the two great chains and some transverse ranges, they run nearly north by east to the Colombian frontier where another “knot” or junction occurs. The summits of the western range form a line of noteworthy regularity, but those of the eastern form a broken irregular line of varying distances from the first. The elevated plateau between the two great chains, which is about 300 m. long and 20 to 30 m. wide, is divided into three great shallow basins or plains by the transverse ridges or paramos of Tiupullo and Azuay. These are known as the Quito, Ambato and Cuenca basins. South of the latter is the irregular and deeply broken Loja basin, which can hardly be considered a part of the great Ecuador plateau. The three great basins, which are broken and subdivided by mountainous spurs and ridges, descend gradually toward the south, the Quito plain having an average elevation of 9500 ft. above the sea, Ambato 8500, and Cuenca 7800. They are also characterized by the increasing aridity of the plateau from north to south, the Quito plain being fertile and well covered with vegetation, and the Ambato and Cuenca plains being barren and desolate except in some favoured localities. The volcanic character of the region is likewise responsible for large areas of barren surfaces. Rising from this elevated plateau, along its eastern and western margins, are the Cordilleras with their principal summits culminating far above the line of perpetual snow, which in this region is about 15,750 ft. above the sea. These summits are remarkable, not only for their great height, but also for their apparent symmetrical arrangement in parallel lines, sometimes in pairs facing each other across this cyclopean passage. Nowhere in the world can there be found another such assemblage of snow-clad peaks, several of which are active volcanoes. There are 22 of them grouped around these central plains almost within sight of each other. The western chain has the distinction of having the highest summit, the eastern the greatest number of high summits and the highest average elevation. From the time of Humboldt’s visit to this remarkable region down to the present time there have been many diverse calculations of the height of these peaks, but with a considerable variation. It is estimated that there was a considerable decrease in the elevation of this part of the Andes during the past century, Quito having sunk 26 ft. in 122 years, Pichincha 218 ft. in the same time, and the farm of Antisana, where Humboldt resided for a time, 165 ft. in 64 years. At the same time Cotopaxi and Sangay, the two active volcanoes, have actually increased in elevation since the measurement of La Condamine in 1742. These changes in elevation, if correct, are due to seismic disturbances, a cause that may be partially responsible for the varying computations of the heights of these well-known peaks. Among modern investigators are W. Reiss and A. Stübel (1871–1873), and Edward Whymper (1880), whose measurements of the principal summits were:— 