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 steamer “Napo” in 1868, it is a vast rent in the Andes about 2000 ft. deep, narrowing in places to a width of only 100 ft., the precipices “seeming to close in at the top.” Through this dark cañon the Marañon leaps along, at times, at the rate of 12 m. an hour. The Pongo de Manseriche was first discovered by the Adelantado Joan de Salinas. He fitted out an expedition at Loxa in Ecuador, descended the Rio Santiago to the Marañon, passed through the perilous Pongo in 1557 and invaded the country of the Maynas Indians. Later, the missionaries of Cuenca and Quito established many missions in the Pais de los Maynas, and made extensive use of the Pongo de Manseriche as an avenue of communication with their several convents on the Andean plateau. According to their accounts, the huge rent in the Andes, the Pongo, is about five or six m. long, and in places not more than 80 ft. wide, and is a frightful series of torrents and whirlpools interspersed with rocks. There is an ancient tradition of the savages of the vicinity that one of their gods descending the Marañon and another ascending the Amazon to communicate with him, they opened the pass called the Pongo de Manseriche. From the northern slope of its basin the Amazon receives many tributaries, but their combined volume of water is not nearly so great as that contributed to the parent stream by its affluents from the south. That part of Brazil lying between the Amazon and French, Dutch and British Guiana, and bounded on the west by the Rio Negro, is known as Brazilian Guiana. It is the southern watershed of a tortuous, low chain of mountains running, roughly, east and west. Their northern slope, which is occupied by the three Guianas first named, is saturated and river-torn; but their southern one, Brazilian Guiana, is in general thirsty and semi-barren, and the driest region of the Amazon valley. It is an area which has been left almost in the undisturbed possession of nomadic Indian tribes, whose scanty numbers find it difficult to solve the food problem. From the divortium aquarum between French Guiana and Brazil, known as the Tumuc-humac range of highlands, two minor streams, the Yary and the Parou, reach the Amazon across the intervening broken and barren tableland. They are full of rapids and reefs.

The is the first river of importance we meet on the northern side as we ascend the Amazon. Its confluence with this is just above the town of Obidos. It has its sources in the Guiana highlands, but its long course is frequently interrupted by violent currents, rocky barriers, and rapids. The inferior zone of the river, as far up as the first fall, the Porteira, has but little broken water and is low and swampy; but above the long series of cataracts and rapids the character and aspect of the valley completely change, and the climate is much better. The river is navigable for 135 m. above its mouth.

The, the great northern tributary of the Amazon, has its sources along the watershed between the Orinoco and the Amazon basins, and also connects with the Orinoco by way of the Casiquiare canal. Its main affluent is the Uaupes, which disputes with the headwaters of the Guaviari branch of the Orinoco the drainage of the eastern slope of the “oriental” Andes of Colombia. The Negro is navigable for 450 m. above its mouth for 4 ft. of water in the dry season, but it has many sandbanks and minor difficulties. In the wet season, it overflows the country far and wide, sometimes to a breadth of 20 m., for long distances, and for 400 m. up, as far as Santa Isabella, is a succession of lagoons, full of long islands and intricate channels, and the slope of the country is so gentle that the river has almost no current. But just before reaching the Uaupes there is a long series of reefs, over which it violently flows in cataracts, rapids and whirlpools. The Uaupes is full of similar obstacles, some fifty rapids barring its navigation, although a long stretch of its upper course is said to be free from them, and to flow gently through a forested country. Despite the impediments, canoes ascend this stream to the Andes.

. In 1744 the Jesuit Father Roman, while ascending the Orinoco river, met some Portuguese slave-traders from the settlements on the Rio Negro. He accompanied them on their return, by way of the Casiquiare canal, and afterwards retraced his route to the Orinoco. La Condamine, seven months later, was able to give to the French Academy an account of Father Roman’s extraordinary voyage, and thus confirm the existence of this wonderful waterway first reported by Father Acuña in 1639. But little credence was given to Father Roman’s statement until it was verified, in 1756, by the Spanish Boundary-line Commission of Yturriaga y Solano. The actual elevation of the canal above sea-level is not known, but is of primary importance to the study of the hydrography of South America. Travellers in general give it at from 400 to 900 ft., but, after much study of the question of altitudes throughout South America, the writer believes that it does not exceed 300 ft. The canal connects the upper Orinoco, 9 m. below the mission of Esmeraldas, with the Rio Negro affluent of the Amazon near the town of San Carlos. The general course is south-west, and its length, including windings, is about 200 m. Its width, at its bifurcation with the Orinoco, is approximately 300 ft., with a current towards the Negro of three-quarters of a mile an hour; but as it gains in volume from the very numerous tributary streams, large and small, which it receives en route, its velocity increases, and in the wet season reaches 5 and even 8 m. an hour in certain stretches. It broadens considerably as it approaches its mouth, where it is about 1750 ft. in width. It will thus be seen that the volume of water it captures from the Orinoco is small in comparison to what it accumulates in its course. In flood-time it is said to have a second connexion with the Rio Negro by a branch which it throws off to the westward called the Itinivini, which leaves it at a point about 50 m. above its mouth. In the dry season it has shallows, and is obstructed by sandbanks, a few rapids and granite rocks. Its shores are densely wooded, and the soil more fertile than that along the Rio Negro. The general slope of the plains through which the canal runs is south-west, but those of the Rio Negro slope south-east. The whole line of the Casiquiare is infested with myriads of tormenting insects. A few miserable groups of Indians and half-breeds have their small villages along its southern portion. It is thus seen that this marvellous freak of nature is not, as is generally supposed, a sluggish canal on a flat tableland, but a great, rapid river which, if its upper waters had not found contact with the Orinoco, perhaps by cutting back, would belong entirely to the Negro branch of the Amazon. To the west of the Casiquiare there is a much shorter and more facile connexion between the Orinoco and Amazon basins, called the isthmus of Pimichin, which is reached by ascending the Terni branch of the Atabapo affluent of the Orinoco. Although the Terni is somewhat obstructed, it is believed that it could easily be made navigable for small craft. The isthmus is 10 m. across, with undulating ground, nowhere over 50 ft. high, with swamps and marshes. It is much used for the transit of large canoes, which are hauled across it from the Terni river, and which reach the Negro by the little stream called the Pimichin.

The. West of the Negro the Amazon receives three more imposing streams from the north-west&mdash;the Yapurá, the Iça or Putumayo, and the Napo. The first was formerly known as the Hyapora, but its Brazilian part is now called the Yapurá, and its Colombian portion the Caquetá. Barão de Marajo gives it 600 m. of navigable stretches. Jules Crevaux, who descended it, describes it as full of obstacles to navigation, the current very strong and the stream frequently interrupted by rapids and cataracts. It rises in the Colombian Andes, nearly in touch with the sources of the Magdalena, and augments its volume