There are few islands on the coast of Colombia, and the great majority of these are too small to appear on the maps in general use. Gorgona is one of the larger islands on the Pacific coast, and is situated about 25 m. from the mainland in lat. 3° N. It is 534 m. long by 134 m. wide, and rises to an extreme elevation Islands. of 1296 ft. above sea-level. It is a beautiful island, and is celebrated as one of Pizarro’s stopping places. It has been used by the Colombian government for political offenders. Malpelo island, 282 m. west by south of Charambira point, in lat. 3° 40′ N., long. 81° 24′ W., nominally belongs to Colombia. It is a small, rocky, uninhabited island, rising to an elevation of 846 ft. above the sea, and has no ascertained value. The famous Pearl islands of the Gulf of Panama are claimed by Colombia, and their pearl oyster fisheries are considered a rentable asset by the government. The group covers an area of about 450 sq. m., and consists of 16 islands and several rocks. The largest is Rey Island, which is about 17 m. long, north to south, and 8 m. broad, with an extreme elevation of 600 ft. The other larger islands are San José, Pedro Gonzales, Casaya, Saboga and Pacheca. There are several fishing villages whose inhabitants are largely engaged in the pearl fisheries, and a number of cocoa-nut plantations. The islands belong chiefly to Panama merchants. There are several groups of small islands on the northern coast, and a few small islands so near the mainland as to form sheltered harbours, as at Cartagena. The largest of these islands is Baru, lying immediately south of the entrance to Cartagena harbour. North-west of Colombia in the Caribbean Sea are several small islands belonging to the republic, two of which (Great and Little Corn Is.) lie very near the coast of Nicaragua. The largest and most important of these islands is Vieja Providencia (Old Providence), 120 m. off the Mosquito Coast, 412 m. long, which supports a small population.
The rivers of Colombia may be divided, for convenience of description, into three general classes according to the destination of their waters, the Pacific, Caribbean and Atlantic—the last reaching their destination through the Amazon and Orinoco. Of these, the Caribbean rivers are of the greatest economic Rivers. importance to the country, though those of the eastern plains may at some time become nearly as important as transportation routes in a region possessing forest products of great importance and rich in agricultural and pastoral possibilities. It is worthy of note that the principal rivers of these three classes—the Patia, Cauca, Magdalena, Caquetá and Putumayo—all have their sources on the high plateaus of southern Colombia and within a comparatively limited area. The Pacific coast rivers are numerous, and discharge a very large volume of water into the ocean in proportion to the area of their drainage basins, because of the heavy rainfall on the western slopes of the Coast range. The proximity of this range to the coast limits them to short, precipitous courses, with comparatively short navigable channels. The principal rivers of this group, starting from the southern frontier, are the Mira, Patia, Iscuande, Micai, Buenaventura or Dagua, San Juan and Baudo. The Mira has its principal sources in Ecuador, and for a short distance forms the boundary line between the two republics, but its outlets and navigable channel are within Colombia. It has a large delta in proportion to the length of the river, which is visible evidence of the very large quantity of material brought down from the neighbouring mountain slopes. The Patia is the longest river of the Pacific group, and is the only one having its sources on the eastern side of the Western Cordillera. It is formed by the confluence of the Sotara and Guaitara at the point where the united streams turn westward to cut their way through the mountains to the sea. The Sotara or upper Patia rises on the southern slope of a transverse ridge or dyke, between the Central and Western Cordilleras, in the vicinity of Popayan, and flows southward about 120 m. to the point of confluence with the Guaitara. The latter has its sources on the elevated plateau of Tuquerres and flows north-west to meet the Sotara. The canyon of the Patia through the Western Cordillera is known as the “Minima gorge,” and has been cut to a depth of 1676 ft., above which the perpendicular mountain sides rise like a wall some thousands of feet more. The upper course of the Guaitara is known as the Carchi, which for a short distance forms the boundary line between Colombia and Ecuador. At one point in its course it is crossed by the Rumichaca arch, a natural arch of stone, popularly known as the “Inca’s bridge,” which with the Minima gorge should be classed among the natural wonders of the world. There is a narrow belt of low, swampy country between the Cordillera and the coast, traversed at intervals by mountain spurs, and across this the river channels are usually navigable. The San Juan has built a large delta at its mouth, and is navigable for a distance of 140 m. inland, the river flowing parallel with the coast for a long distance instead of crossing the coastal plain. It rises in the angle between the Western Cordillera and a low transverse ridge connecting it with the Baudo coast range, and flows westward down to the valley between the two ranges, and then southward through this valley to about lat. 4° 15′ N., where it turns sharply westward and crosses a narrow belt of lowland to the coast. It probably has the largest discharge of water of the Pacific group, and has about 300 m. of navigable channels, including its tributaries, although the river itself is only 190 m. long and the sand-bars at its mouth have only 7 or 8 ft. of water on them. The San Juan is distinguished for having been one of the proposed routes for a ship canal between the Caribbean and Pacific. At one point in its upper course it is so near the Atrato that, according to a survey by Captain C. S. Cochrane, R.N., in 1824, a canal 400 yds. long with a maximum cutting of 70 ft., together with some improvements in the two streams, would give free communication. His calculations were made, of course, for the smaller craft of that time.
The rivers belonging to the Caribbean system, all of which flow in a northerly direction, are the Atrato, Bacuba, Sinú, Magdalena and Zulia. The Bacuba, Suriquilla or Leon, is a small stream rising on the western slopes of the Cordillera and flowing into the upper end of the Gulf of Uraba. Like the Atrato it brings down much silt, which is rapidly filling that depression. There are many small streams and one important river, the Sinú, flowing into the sea between this gulf and the mouth of the Magdalena. The Sinú rises on the northern slopes of the Alto del Viento near the 7th parallel, and flows almost due north across the coastal plain for a distance of about 286 m. to the Gulf of Morosquillo. It has a very sinuous channel which is navigable for small steamers for some distance, but there is no good port at its outlet, and a considerable part of the region through which it flows is malarial and sparsely settled. The most important rivers of Colombia, however, are the Magdalena and its principal tributary, the Cauca. They both rise on the high table-land of southern Colombia about 14,000 ft. above sea-level—the Magdalena in the Laguna del Buey (Ox Lake) on the Las Papas plateau, and the Cauca a short distance westward in the Laguna de Santiago on the Paramo de Guanacas—and flow northward in parallel courses with the great Central Cordillera, forming the water-parting between their drainage basins. The principal tributaries of the Magdalena are the Suaza, Neiva, Cabrera, Prado, Fusagasaga, Funza or Bogotá, Carare, Opon, Sogamoso, Lebrija and Cesar, and the western the La Plata, Paez, Saldaña, Cuello, Guali, Samana or Miel, Nare or Negro and Cauca. There are also many smaller streams flowing into the Magdalena from both sides of the valley. Of those named, the Funza drains the “sabana” of Bogotá and is celebrated for the great fall of Tequendama, about 480 ft. in height; the Sogamoso passes through some of the richest districts of the republic; and the Cesar rises on the elevated slopes of the Sierra Nevada de Santa Marta and flows southward across a low plain, in which are many lakes, to join the Magdalena where it bends westward to meet the Cauca. The course of the Magdalena traverses nine degrees of latitude and is nearly 1000 m. long. It is navigable for steamers up to La Dorada, near Honda, 561 m. above its mouth, which is closed by sand-bars to all but light-draught vessels, and for 93 m. above the rapids at Honda, to Girardot. The river is also navigable at high water for small steamers up to Neiva, 100 m. farther and 1535 ft. above sea-level, beyond which point it descends precipitously from the plateaus of southern Colombia. The Honda rapids have a fall of only 20 ft. in a distance of 2 m., but the current is swift and the channel tortuous for a distance of 20 m., which make it impossible for the light-draught, flat-bottomed steamers of the lower river to ascend them. The Cauca differs much from the Magdalena, although its principal features are the same. The latter descends 12,500 ft. before it becomes navigable, but at 10,000 ft. below its source the Cauca enters a long narrow valley with an average elevation of 3500 ft., where it is navigable for over 200 m., and then descends 2500 ft. through a series of impetuous rapids for a distance of about 250 m., between Cartago and Cáceres, with a break of 60 m. above Antioquia, where smooth water permits isolated navigation. While, therefore, the Magdalena is navigable throughout the greater part of its course, or from Girardot to the coast, with an abrupt break of only 20 ft. at Honda which could easily be overcome, the Cauca has only 200 m. of navigable water in the upper valley and another 200 m. on its lower course before it joins the Magdalena in lat. 9° 30′, the two being separated by 250 m. of canyon and rapids. So difficult is the country through which the Cauca has cut its tortuous course that the fertile upper valley is completely isolated from the Caribbean, and has no other practicable outlet than the overland route from Cali to Buenaventura, on the Pacific. The upper sources of the Cauca flow through a highly volcanic region, and are so impregnated with sulphuric and other acids that fish cannot live in them. This is especially true of the Rio Vinagre, which rises on the Purace volcano. The principal tributaries are the Piendamó, Ovejas, Palo, Amaime and Nechi, from the central Cordillera, of which the last named is the most important, and the Jamundi and a large number of small streams from the Western. The largest branch of the Cauca on its western side, however, is the San Jorge, which, though rising in the Western Cordillera on the northern slopes of the Alto del Viento, in about lat. 7° N., and not far from the sources of the Sinú and Bacuba, is essentially a river of the plain, flowing north-east across a level country filled with small lakes and subject to inundations to a junction with the Cauca just before it joins the Magdalena. Both the San Jorge and Nechi are navigable for considerable distances. The valley of the Cauca is much narrower than that of the Magdalena, and between Cartago and Cáceres the mountain ranges on both sides press down upon the river and confine it to a narrow canyon. The Cauca unites with the Magdalena about 200 m. from the sea through several widely separated channels, which are continually changing through the wearing away of the alluvial banks. These changes in the channel are also at work
