Graham's Magazine, Vol. XLI, No. 6, December 1852. Various
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Название: Graham's Magazine, Vol. XLI, No. 6, December 1852
Автор: Various
Издательство: Public Domain
Жанр: Журналы
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The Volga is celebrated for its seventy mouths; and the Ganges, the Nile, Mississippi, and Orinoco pour out their current through several branches. The space inclosed within these various channels is called a delta, from its triangular form, and general resemblance to the shape of the Greek letter Δ. So powerfully do many of the great rivers rush into the ocean, that their waters are distinct from those of the briny deep, when out of sight of the land. A British fleet lying opposite to the mouth of the Rhone occasionally took up fresh water at a considerable distance from the shore; and Columbus found his vessel in the fresh water of the Orinoco before he discovered the continent of South America. The collision of a great river current and the opposing tide of the sea is sometimes so violent as to occasion an elevated ridge of waters, heaving and tossing in a tremendous manner, shattering to pieces the ill-fated vessel that comes into contact with it. The passage of the Garonne into the Bay of Biscay, and of the Ganges into the Bay of Bengal, exhibit this phenomenon.
In treating of the magnitude of rivers, some writers refer to the elevation of the range of mountains from which they descend; and it is obviously true, that the greater the height of the mountains, the more extensive are their snows and glaciers, and the larger the supply of water furnished by springs and torrents. But the magnitude of a stream is more especially regulated by the extent of country which forms the declivities of its basin, though there is no invariable proportion here, for a small basin in a humid region will yield a greater quantity of water than one much more considerable in a different situation. High mountains, a humid climate, and a wide superficial drainage, are the three physical circumstances which lead to the accumulation of vast bodies of water, the magnitude of which will be proportionate to the degree in which these causes are in combined operation. Upon the surface of the New World, we have these causes acting with greater intensity than upon that of the Old, which explains the superior character of the streams of the western continent. The following exhibits the extent of the hydrographical regions of the principal rivers of the globe, with the proportionate quantity of their waters:
Malte Brun estimates that, representing all the waters discharged by the European rivers by unity, the Black Sea receives 0·273; the Caspian, 0·165; the Mediterranean, Sea of Marmora, and Archipelago, 0·144; the Atlantic Ocean, 0·131; the Baltic, 0·129; the North Sea, 0·110; the Arctic Frozen Ocean, 0·048. The annexed table has a character of universal interest, and naturally finds a place here.
The first place among the rivers of the globe is due to the Amazon, if not for the length of its course, yet for the volume of its waters. It traverses the equatorial regions of South America, chiefly in a direction from west to east, and has its embouchure nearly under the equator. Its mouth was discovered in the year 1500 by Pinzon, one of the captains who sailed with Columbus on his first voyage; and thirty nine years afterward, the stream was traced downward from Peru by Francisco Orellana, whose name was given to the river by his countrymen, to preserve the memory of his bold enterprise. But the Spaniard’s report of having met with armed women on its banks, deprived him of the honor, for it originated the common title of the river of the Amazon. Its principal affluents rival the largest rivers of the Eastern continent, as appears from the following statement of their supposed lengths —
The width of the Amazon averages from one to two miles in the upper parts of its course, but toward its termination its opposite banks are seen with difficulty, and it widens to between twenty and thirty miles, which is about its breadth upon joining the Atlantic. For two thousand miles in a direct line from the ocean, the river is navigable by vessels of any burden; for, at the confluence of the Tunguragua and Ucayali, where the Amazon – properly so called – commences, no bottom was found in March, 1836, with a line of 35 fathoms, or 210 feet. The tide rushes up its channel with immense violence at the period of the full moon, in two, three and sometimes four successive waves, each presenting a perpendicular front of from ten to fifteen feet. When the tide ebbs in the rainy season, the liberated waters of the river rush out of their channel with tremendous force, and create a current in the ocean, which is perceptible five hundred miles from its mouth. It is difficult to sound the river, owing to the rapidity of its current, which runs commonly at the rate of from three to four miles an hour – a momentum not arising from the inclination of its bed, the fall of which is very gradual, but from the immense quantity of water which descends in it. The climate of its basin is, perhaps, the most humid to which any country is subject. The quantity of rain which annually descends upon this region, has not been ascertained with precision; but taking that at the town of Maranhão as a sample, which is not less than two hundred inches, the amount of rain poured upon the district of the Amazon every year must be prodigious. The heat also is excessive through the whole year, the thermometer in the shade frequently rising to 106° when the sun is near the line, a degree of heat not much inferior to that experienced in the Sahara; and as moisture and heat are the most efficient agents in promoting vegetation, hence the luxuriance and energy of vegetable life in the fertile soil on the banks of the river, where the noblest woodland scenery in the world is to be found. Notwithstanding the rapid current of the Amazon, its navigation is easy to vessels both descending and ascending its course, the ascent being facilitated by the far-penetrating tide of the Atlantic, assisted by the wind, which is always blowing from the east, a direction contrary to that of the stream. But the effect of the presence and absence of civilization is nowhere more strikingly exhibited than on the waters of the South American river, and those of its rivals, the Mississippi, and the Yang-tse-Kiang of the Chinese empire. The vessels that annually appear upon the surface of the Amazon are, probably, not more than those which monthly navigate the Mississippi, or daily pass along the course of the Yang-tse-Kiang.
At the head of rivers, classed according to their length, the Mississippi is to be placed, taking the Missouri branch, which ought to be the name of the united stream, not only on account of its longer course, but because it brings down a greater body of water, and imparts its turbid character to its rival. Geographers have, however, given the former name to the joint rivers, the “Father of Waters,” according to its Indian signification, which may be aptly applied to the great central valley of North America, furnishing the following streams, which unite in the channel of the Lower Mississippi, and pour down through it into the Gulf of Mexico —
The most beautiful tributary of the Mississippi is the Ohio, the Belle rivière of the early French settlers, the only large river it receives from the east. No stream rolls for the same distance so uniformly and peacefully; its banks are adorned with the largest sycamores, its waters СКАЧАТЬ