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Graham's Magazine, Vol. XLI, No. 6, December 1852. Various
Читать онлайн.Название Graham's Magazine, Vol. XLI, No. 6, December 1852
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“Pure element of waters! wheresoe’er
Thou dost forsake thy subterranean haunts,
Green herbs, bright flowers, and berry-bearing plants,
Rise into life, and in thy train appear.”
Upon the large circular valley-plain of Bœotia, the heights of Parnassus on the west, Helicon on the south, and Cithæron on the east, send down streams, covering the undulating surface of this Classic Land with a life-sustaining vegetation.
The same physical causes – high lands and the contiguous sea – operate, in Judea as in Greece, to render it a well-watered country – a “land of brooks,” according to its Scripture designation. There are no considerable rivers, owing to the scanty extent of its hydrographical basins; but the melting of the snow on the high mountains of Syria, and the periodical sound of an “abundance of rain,” contribute to furnish an ample irrigation. Its principal stream – the Jordan – though only one of the fifth class, and not remarkable for picturesque beauty except in the upper part of its course, has a sacred and historic interest, which will always strongly attract attention to it, while it exhibits a singular physical peculiarity. This is the depression of the valley, in which it flows, below the level of the Mediterranean, through the whole distance between the Sea of Tiberias and the Dead Sea; and the great inclination of its descent from the one to the other, amounting at a mean to very nearly eighteen feet per mile. Hence the force of its current, notwithstanding a comparatively small volume of water, and the few windings that mark its channel. Speaking of its appearance near the site of Jericho, Dr. Robinson states: “There was a still though very rapid current. We estimated the breadth of the stream to be from eighty to one hundred feet. The guides supposed it now to be ten or twelve feet deep. The current was so strong, that even Komeh, a stout swimmer of the Nile, was carried down several yards in crossing.” Upon the authority of some phrases in the English version of the Scriptures, which, perhaps, do not express the sense of the original Hebrew, it has been generally supposed that the Jordan periodically inundated the country in its neighborhood, at, and for some time after, the Israelitish conquest of it. If this were so, either the river must have worn for itself a deeper bed, or the quantity of rain in Palestine must have largely diminished, for there is now no overflow of its banks. At present, the “swellings of Jordan” – one of the phrases alluded to – amount only to a slight annual rise. Copious rains descend upon the mountains round its sources, and the melting of the snows of Lebanon supply numerous temporary torrents; but these contributions are received into the capacious basins of the lakes Merom and Tiberias, and are there spread over an extensive surface, so as to prevent the level of the river from rising into inundation.
In exactly the same manner, the great Canadian lakes, prevent any rise to the St. Lawrence, by the immense floods that rush into them in the spring spreading over their vast beds, and producing only an almost inappreciable elevation of their level. Lebanon, the feeder of the Jordan from its internal reservoirs, along with “Abana and Pharpar, rivers of Damascus,” and the Orontes, gives birth to many rapid and brawling streams, and a thousand cascades, when its snows melt, which strikingly display the erosive power of running water. Deep passages have been cut in the rocks, bestrided by natural arches, like the rock-bridge of Virginia. Of this description is the natural bridge over the Ain el Leban, rising nearly two hundred feet above the torrent which has gradually dug the excavation, as annually the spring has renewed its strength. The brook flows into the Beyrout river, and its channel would be quite dry in summer, were it not for the impediments its mountain course presents. It was the spring season, the time of the melting of the snow, when the monarch of Israel, during his temporary exile from the throne, retreated for a refuge toward the fastnesses of Lebanon. He saw the torrents falling from height to height into the valleys. He heard the voices of the waters as they leaped from rock to rock. His imagination converted this external scenery into a picture of the force of his adversities; and hence the allusion, in the plaintive elegiac, commemorative of his condition, to the “noise of cataracts,” and to “deep calling unto deep.”
In advancing toward their termination, and at their embouchure, the great rivers present several striking peculiarities. It has already been remarked, that a junction of two large streams often occurs without any expansion of the surface of their waters being the consequence, but a greater velocity of current and depth of channel. In some cases, instead of a wider course being created by increased volume of water, there is actually a narrower bed. Thus the Mississippi is a mile and a half wide, and the Missouri half a mile wide, at their confluence, yet from that point to the mouth of the Ohio, the medium width of the united rivers is but three-quarters of a mile, and through the lower parts of its course the main stream has, if any thing, a less surface-breadth, though vast accessions are made to it by the Arkansas, Red River, and others of great depth and body of water. Most of the tributaries of the Mississippi also, are wider a thousand miles apart from it than at the point of junction, and the same feature is characteristic of other great streams, that as they increase their volume of water and approach their termination, they flow in narrower though deeper channels. The Nile is not so broad at Cairo as at Siout, nor so broad at Siout as at Thebes. At Assouan, high up the stream, it is 3900 feet wide; at Oudi, 36 miles above Cairo, it is 2900; and at Rosetta, near its mouth, but 1800. This is one of the many examples of benign adjustment with which the realms of nature teem; for hereby a rich legacy of fertile soil, usually found at the mouths of rivers, is saved from submergence, and becomes the inheritance of man. In their junction with the sea, rivers display the diversity of sometimes pouring forth their waters through a single mouth, and distributing them into a variety of channels; circumstances mainly dependent upon the country through which they flow being easily susceptible of excavation or not, and upon the power of the stream. The Ganges pours its flood through the many channels here represented.
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