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Show 298 SALT IN TilE MEDITERRANEAN. PRECIPITATION OF . h L' an essential difference between d S There ls, oweve ' . bl Dea ea. . for t 1 M d't rranean is not only mcompara y 1C e I e . b . these cas· es ' xtent t l1 an t 11 e two last-mentioned ba.s ms, ut Its 1 . greater. m e In the narrowest part of t 1e Stratts depth IS enormous. th are about nine miles broad, be-of Gibraltar, whereTar~~a and Alcanzar Point, the depth tween the Isle of d d 1 sixty to £ ve hundred fathoms; . f one hun re an( d d vanes rom d C uta Captain Smyth soun e to b t Gibraltar an c ' 1 1 but e ween. e th of nine hundred and fifty fat ~oms. the extmordmary d P ll b ttom with fraO'ments of broken 1 f, nd a grave y o ' b d where 1e ou d d t the depth of two thousan 1 11 Saussure soun e o . Wl s lC s. d f the shore at NICe. Jat pro-feet, within a few yar 8 0 pect so~e of the central abysses .r tl en may we not ex b ~ funulty' 1 ' l I 'I'h evaporation being, as we eiOI'e f 1 · a to reac 1 . e · d o t us se . 1 f ce water becomes Impregnate d ·y rapid t 1e sur a . . I stale ' ~er ' of salt. and its specific gravity bemg t ms with a shgl~t ~xcess 1 fall~ to the bottom, while lighter water increased, It mstant1y . d ced by rivers and by the currises to the top, or t 1at mfltro u r it Bu~ the heavier fluid f t1 Atlantic ows ove . 1 rent rom 1 e 'h b tt but flows on till it reac 1es does not merely fall to t ef oh om, bmarine basins into which 1 ·t of one o t ose su . 'd d the owest par f tl is inland sea to be dlVl e . the bottom o 1 · f we must suprose f this process, additional supphes o By the contmuance o ,. d t deep repositories, until the . nnually carne o .. ti brme are a . full saturated, and preCipita on lower strata of ~ate~. ar~l y such as are said to cover the takes place-not m t ~~ m~, rn shores of the Euxine, nor alluvial marshes along t e we; ~ lt "ctangs '' of the Rhone, in minute layers, like those o t 1et. sa ous masses of pure rock· l dest scale-con mu h l'k but on tle . gran for hundreds of miles in lengt ' 1. e salt, extendmg, perh~ps, f p 1 d Huncrary, Transylvanta, t ll OSe l·n the mountams o o an ' b and Spain*. . t fl wing westward, none of the CX· * As to the existence of an infen?r currenoun~enauce whatever to this popular . nts made in the late survey glve any c rt t it not only because the cx~e~· per~me _, l·t seems most unnecessary to rcso ot b' 'mtnense but because It IS nohon · anu · f on mus c 1 ' · b dth diture ~f the :~~d~tet~:~~:;~1ia~~r:;a~:;r:1~ts,' which conj~int~/~~~~~!b~~. r~hey not yet prove t. a do not restore the equilibl'i urn, if occast:o~~: the west than to the that of the cen te, arry more wa cr d . to the ebb and flow with the tid~, but the.~;ay fc tbe Straits tbe water rcturne lll t Tbe opinion, that 1n the JJll e 0 e~. . FLOATING ICEBERGS. 299 The Straits of Gibraltar are said to become gradually wider by the wearing down of the cliff's on each side at many points; and the current sets along the coast of Africa so as to cause considerable inroads in various parts, particularly near Carthage. Near the Canopic mouth of the Nile, at Aboukil·, the coast was greatly devastated in the year 1784, when a small island was nearly consumed. By a series of similar operations, the old site of the cities of Nicopolis, Taposiris, Parva, and Canopus, have become a sandbank*. Floating Icebergs.-Marine currents are sometimes instrumental in the transportation of rock and soil, by floating large masses of ice to great distances from the shore. When glaciers in nort.hern latitudes descend the va1leys burdened with alluvial debris, and arrive at the shore, they are frequently detached, and float off'. Scoresbyt counted five hundred icebergs in latitude 69° and 70° north, rising above the surface from the height of one to two hundred feet, and measuring from a few hundred yards to a mile in circumference. Many of these contained strata of earth and stones, or were loaded with beds of rock of great thickness, of which the weight was conjectured to be from fifty thousand to one hundred thousand tons. As the mass of ice below the level of the water is between seven and eight times gt·eater than that above, these masses rna y sometimes take the ground in great numbers, in particular parts of the sea, and may, as they dissolve, deposit such masses of matter on particular parts of the bottom of the deep, or on the shores of some isles, as may offer perplexing problems to future geologists. Some ice islands have been known to drift from Baffin's Atlantic by a submarine counter-current, first originated in the following circum· stance. M. Du 1' Aigle, commander of a privateer called the Phoonix, of Marseilles, gave chase to a Dutch merchant ship, near Ceuta Point, aud came up with her in the middle of tho gut, between Tariffa and Tangier, and there gave her one broadside, which directly sw1k her. A few days after, the sunk ship, with her cargo of brandy and oil, arose on the shore near Tangier, which is at least four leagues to the westward of the place where she sunk, and directly against the strength of the central curn•nt.-Phil. Trans., 1724. It seems obvious that the ship in this case was brought back by one of the late1·at currents, not by an under current. ; . Clarke's Travels in Europe, Asia, and Africa, vol. iii., pp. 340 and 363, 4th edthon, t Voyage in 1822, p. 233, |