The average depth of the Amazon river is 42 feet in the upper portion, and 312 feet near to its mouth. The influence of the tide is observable at a distance of 400 miles from the mouth of the river, the usual current of which is about three miles per hour. The flood rise is from 42 to 48 feet above the lowest level. At a distance of 3000 miles from its mouth the Amazon is only 210 feet above sea level. Reclus has estimated the average discharge of the river to be 2,458,026 cubic feet per second.[123]

The Magdalena River.—The river in Columbia known by the name of the Magdalena has its rise in the Lagunas de las Papas (Potato Lake), and is one of the boundary lines of six of the nine States into which Columbia is divided. The river runs nearly due north from its source until it empties into the Carribean Sea in latitude 10° 59´ north, and 70° 58´ west longitude. The length of the river, measured on a meridian, would be 569 miles, but according to the best information available the actual length of the stream is about 900 miles. The Boca de Ceniza is the only mouth of the stream open to navigation, the depth of water on the bar here varying from 10 to 20 feet. It has been proposed to construct jetties at the mouth, so that it would be navigable to the largest ships frequenting this part of the world. A channel of 40 to 60 feet in depth can be found for a distance of about 20 miles inside the bar.

Natural obstacles have compelled the navigation of the river to be divided into five different systems—the first, rafts and canoes from Bateas to Neiva; the second, steamboats, barges, rafts, and canoes from Neiva to La Noria; the third, steamboats, barges, and canoes from Caracoli to Barranquilla; and the fourth, barges, sailing ships, and small ocean steamers from Barranquilla to the ocean.

It was not until 1847 that a really successful attempt was made to navigate the Magdalena by steam. Between that year and 1852 four steamers, of American build, were placed on the river. Now there are twenty-seven steamers regularly employed, besides a fleet of barges.

The natural obstacles to navigation at the bar of the river have led the Government of Columbia at different times to expend considerable sums of money in trying to open a canal from the river at Calawar to Carthagena, known as the Dique. The project has not, however, been very successful. The distance of this route is about 90 miles, and, although the four steamers employed upon it by the Dique Company have been tolerably successful, a large expenditure is said to be still required to complete the means of transport. As it is, the Government have dredges constantly at work on this artificial waterway. The Government are, moreover, canalising the river throughout its entire length, the cost being defrayed by charges on the traffic, which is steadily increasing.[124]

The Desague Real de Huchuetoca.—This is a vast drain or cut that has been carried through the Cordilleras, that surround the Valley of Tenochillan, or Mexico, at Nochistongo, for the purpose of getting rid of the dreadful inundations which almost periodically came upon the city of Mexico. The Section of the Desague, for a considerable distance, is from 1800 to 3000 square metres (19,365 to 32,275 sq. feet). Its length from Vertideres to the Salts is 20,585 metres, or 67,535 feet. Near the old well of Don Juan Garcia, at the point where the ridge is highest, the cut in the mountain extends for a length of more than 2624 feet, to between 147 and 196 feet in perpendicular depth. For a length of over 3000 feet more, the depth of the cut is from 98 to 131 feet. Over a great part of the cut, however, the breadth is said to be by no means in proportion to its depth, so that the sides are much too steep and are every now and again falling in.

The Desague was constructed between 1607 and 1650, and with its dykes and two canals leading from the upper lakes, is stated to have cost 31,000,000 of livres, or 1,291,770l. According to Humboldt, however, 25,000,000 of livres “were expended because they never had the courage to follow the same plan, and because they kept hesitating for two centuries between the Indian system of dykes and that of canals—between the subterraneous gallery and the open cut through the mountain.” Humboldt adds that “they neglected to finish the cut of Nochistongo, while they were disputing about the project of a canal of Tezaico, which was never executed.” The meaning of Humboldt’s reference to the cost of this undertaking is rather obscure. One writer has pointed out that if he means that the necessary cost of the work was only 6,000,000 livres, or 250,000l., there falls to be deducted from this amount the cost of two other canals—those of Zampango and San Christobal, begun in 1796 and 1798—amounting to 41,670l. more.[125] This, however, is not at all likely to be Humboldt’s meaning, since he elsewhere speaks of the Desague as “undoubtedly one of the most gigantic operations ever executed by man,” and looks upon it with “a species of admiration, particularly when we consider the nature of the ground, and the enormous breadth, depth, and length of the aperture.” The magnitude of the undertaking may be appreciated by the fact, mentioned also by Humboldt, that if the Desague were filled with water to the depth of 10 metres (32 feet), the largest vessels of war could pass through the range of mountains which bound the plain of Mexico to the north-east.

Of the other rivers in South and Central America none call for any special description. Few of them are navigable for any distance, being—like the Chagres river, which traverses the Isthmus of Panama, or the San Juan river, that is to be utilised for the Nicaraguan canal—too rapid, tortuous and subject to floods, to be convenient for purposes of navigation. In course of time, however, as wealth and population increases, we may naturally look for the artificial improvement of such waterways with a view to their adaptation for purposes of commerce, as in the European rivers already referred to.

FOOTNOTES
CHAPTER XVII

[123] Van Nostrand’s ‘Magazine,’ vol. xxiv. p. 66.