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Show 184 EMBANKMENTS OF PO AND ADIGE. bed called "Po Vecchio," can·yinO' away three streets of Casalmaggiore. The friars in the mo~astery de' Serviti took the alarm in 1471, demolished their buildings, and reconstructed them at Fontana, whither they had transported the materials. In like manner, the church of S. Rocco was demolished in 1511. In the seventeenth century also the Po shifted its course for a mile in the same district, causing great devastations >X'. To check these and similar aberrations, a general system of embankment has been adopted; and the Po, Adige, and almost all their tributaries, are now confined between high artificial banks. The increased velocity .acquired by streams thus closed in, enables them to convey a much larger portion of foreign matter to the sea; and consequently the deltas of the Po and Adige have gained far more rapid] y on the Adriatic since the practice of embankment became almost universal. But although more sediment is borne to the sea, part of the sand, and mud, which in the natural state of things would be spread out by annual inundations over the plain, now subsides in the bottom of the river-channels, and their capacity being thereby diminished, it is necessary, in order to prevent inundations in the following spring, to extract matter from the bed, and to add it to the banks, of the river. Hence it has arisen that these streams now traverse the plain on the top of high mounds, like the waters of aqueducts, and the surface of the Po has become more elevated than the roofs of the houses of the city of Ferrara t. The magnitude of these barriers is a subject of increasing expense and anxiety, it having sometimes of late years been found necessary to give an additional height of nearly one foot to the banks of the Adige and Po in a single season. The practice of embankment was adopted on some of the Italian rivers as early as the thirteenth century ; and Dante, writing in the beginning of the four· teenth, describes, in the seventh circle of hell, a rivulet of tears separated from a burning sandy desert by embankments "like those which, between Ghent and Bruges, were raised against the ocean, or those which the Paduans had • Dell' Antico Corso de' Fiumi Po, Oglio, ed Addo. dell' Giovanni Romani, :Milan, 1828. t Prony, see Cuvier1 Disc. Frelim., r• 146. llASIN OF 'filE MISSISSIPPI. 185 erected along the Brcnta to defend their vill . of the Alpine snows." as on the meltmg Quale i Fiamminghi tra Guzzanto e B . Tcmcndo il fiotto che in ver lor s' a nttggta, l~ 1 vven a E auno o. schcrmo' P"" rchc t'l mar s1. f uggt·a' qu~Jc 1 Padovan lungo la Brcnta, ' Per ~tfcndcr lor ville e lor castelli, Anzt chc Chiarentana il caldo senta- . • Inferno, Canto xv. Basm of the .Mtssissippi.-The hydrogr·aph' 1 b . M' · · · d' ICa asm of the Iss~ssippl !splays, on the grandest scale the acti £' runnm'fig wate.r on .t he surface of a vas t co' ntm. cnt. oTn hois magm cent river rises nearly in th ~ t . h north latitude, and flows to the Ge lofr yf-mMnt .par~llel o. f t · h u o exiCo m ti wenty-mnt -a course includinO' 't d Ie fi I l . ' o I s mean ers, of nearl ve t 1ousanc miles. It passes fr ld . . Y I om a co arctic chmat ·tr aversIe s t 1e .t emperate 1·egions' an d d1' sc h arO'es I. ts e, t Into t 1e sea, m the region of tl ]' o wa ers sugar-cane*. No river afford le ~Ive,. ~he .fig, and the the law before mentioned tl st a mote stnkm~ Illustration of d ' la an auO'mentation of 1 oes not occasion a proportion 1 . 0 . a mcrease of surf•a c vo um.e even sometimes attended with a . f e, nay, IS Mississippi is a mile and a halfnar~dowmg .o t!le channel. The Wl e at Its J t' · h Missouri, the latter beinO' half '1 'd unc Ion Wit the waters have only from th . fla mi e WI e; yet the united 01 . ' eir con uence to the th f no, a medial width of ab t th mou o the · · ou ree quarters of 'I Tl JUnction of the Ohio seem l a ml e. le rather a decrease of f.s a tso to produce no increase, but Arkansas and Red . sur ace . The St. Francis, White stream with scarcely arniyvearps,pare tal.so absorbed by the mai~ aren mcreas f · t 'd on arriving near the sea at N" e .o .I s Wl th; and, than half a mile wide It dew Orleans,. It Is somewhat Jess greatest at hio-h wate~ b .s epth thhere Is very variable, the ~ 0 emg one undred d · · Iect. The mean rate at h' h h an Sixty-eight is variously estimated Aw Ic d~ e whole body of water flows, . ccor InO' to som 't d one mile an hour + Tl II . ol . e, I oes not exceed b d +· lea UVIa plam of th' . oun ed . on the east a d b IS great nver is stretching along th . n we~t y great ranges of mountains ,.. eir respective oceans · Below th e J. uncti.O n Flin~'s Geography, vol. i., p. 21. . t Halls Travels in North A . ... t lb1d., p. 140. merxca, vol,m., ll· 330, who cites Darby. |