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Show 300 DRIFT SAND, Bay to the Azores, as we before stated, and from the South Pole to the immediate neighbourhood of the Cape of Good Hope. Sand .flills.-It frequently happens, where the sea is encroaching on a coast, that perpendicular cliffs of considerable height, composed of loose sand, supply, as they crumble away large quantities of fine sand, which, being in mid-air when de: tached, are carr~ed by the winds to great distances, covering the land or bnrrmg up the mouths of estuaries. This is exemplified in Poole Bay, in Hampshire, and in many points of the coast of Norfolk and Suffolk. But a violent wind will sometimes drift the sand of a sea-beach, and carry it up with fragments of shells to great heights, as in the case of the sands of Barry, at the nor~hern side of the estuary of the 'l.'ay, where bills of this origin attain the extraordinary height of from two hundred and fifty to three hundred feet. On the coast of France and Holland long chains of these dunes have been formed in many parts, and often give rise to very important geological changes, by barring up the mouths of estuaries, and preventing the free ingress of the tides, or free efflux of river water. The Bay of Findhorn, in Morayshire, has been blocked up in this manner since the beginning of the seventeenth century, so that large vessels can no longer enter; and we have already mentioned changes of a similar kind at Great Yarmouth, in Norfolk. Chains of sand-hills have also accu· mulated on the shores of the delta of the Nile, especially opposite the Lakes of Brulos and Menzala, forming mounds whereby the waters of these lakes are retained*. By the alter· nate formation and destruction of such barriers, fresh-water and marine deposits may sometimes be formed in succession on the same spots, and afterwards be laid dry by the exclusion of the tides, and be again submerged when high tides break into the estuary again. Many of the phenomena of submarine forests may, perhaps, admit of explanation, when the effects of such barriers of sand have been more carefully studied. The loose sand often forms a finn mass when bound together by the roots of plants fitted for such a soil, particularly the Arundo arenaria, and Elymus arenarius. · • Rennell's Herodotus. DE LUC's NATUR AL CHRONOMETERS. 301 A considerable tract of 1 . Cornwall has been inundat:~ t~va~~ land on the ~orth coast of ral hundred feet above th I ~ nft-sand, formmg hills sevecomminuted marine sh 11 e e; of the sea, and composed of ruins of ancient buildin: sl. yb the shifting of the sands the l bs lave een di d ' cases w 1ere they have been b . d scovere ; and, in some strata, separated by a vcg t bfte to a great depth, distinct localities, as at New Q e a] e crust, are visible. In some • 1 uay, arge masses 1 b Cient y indurated to be us d f, lave ecome suffi-lapidification which is st~ll . ot· architectural purposes. The 'd . ' I m progress a b oxi e of 1ron held in solution b tb ' ppears. to e due to the sand*. 'l'errestrial shells a/£ e water whiCh ~er:olates rock. e ound enclosed entire m this The moving sands of the Af . d by the west winds over all th ri~and eserts have been driven the western banks of the N'J e an s capable of tillage on by mountains t 'l'h · Ief' ex.cept such as are sheltered . e rums o anct t ·r these sands between the '.f 1 en CI Ics are buried under Nubia. De Luc attem ted etmP, e£ of Jupiter Ammon and continents, from the facf th to ~n er the recent origin of our o~l~ arrived in modern time: at \:e ~:~~f of ~he desert have 'I his scourge he said w ld 1 e plams of the Nile. t · ' ' ou lave afflicted E t f, an eriOr to the times of history 'f tl . ..gyp or ages the level of.. the sea several h;nidre~ contm~nts had risen above B.ut the author proceeded in thi~ c:ntune~ before our era t. gical computations on I .~a' as m all hts other chronolo- ' a mu titu e of g. t · not one of which he 1 d 1 ta mtous assumptions ought, in the first plaC:,a t t ~ candour to state explicitly. H~ continent of Africa ' ? dave demonstrated that the whole peri.o d ; for unless thw.a s rm. se above the 1e ve1 of t h e sea at one whence the sands b Is pomt was established' the reo·ion from addition made to Afe?an tod move might have bee~ the last fl oo d might have beernic aIo, na(n)' the c. ommencemcnt of the sand-greater portion of th t b. posteriOr to the formation of the Europe were not lla clontment. That the different parts of d · a e evated at 0 · · a mtttcd. De Luc should 1 ne t.Ime, Is now generally a so have pomted out the depth of G *1 B oase on the S ubmerst.o n f t f eo. Society of Cornwall .. o par o the Motmt's Bay, &c. Trans. Roy. t De Luc M ' vol. n., P· 140. ' ercure de France' Sept' 1809 · t Ibid. |