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Show ~04 INFLUENCE OF MAN IN MODIFYING [Ch. XII. t '1 b · interwoven with the roots of grass and uppermos so1 emg . . l 1 t d hardened by the sun, IS capable of With. ot 1er p an s, an . d . 11 tt ks f the river These Islands often grow to stan mg a a ac o · a cons1' d erab le s·t ze, and endure for the lives of the new pos· b · Jy at last destroyed by the same gradual sessors, emg on . . f d rm.tni'ng and encroachment to whiCh the banks process o un e ~ of the Ganges are su b~. ec~ * · . . If Bengal were inhabited .by a natl?n more advanced m opulence and agricultura~ sk1ll, ~hey m1ght, perhaps, succeed in defending these possessions agamst the ravages of the stream for much longer periods; but no human power could ever prevent the Ganges, or the Mississippi, from making and unmaking islands. By fortifying one spot against the set of the current, its force is only diverted against some other point; and after a vast expense of time and labour, the property of individuals may be saved, but no addition would thus be made to the sum of productive land. It may be doubted, whether any system could be devised so conducive to national wealth, as the simple plan pursued by the peasants of Hindostan, who, wasting no strength in attempts to thwart one of the great operations of nature, permit the alluvial surface to be perpetually renovated, and find their losses i~ one place compensated in some other, so t~at. the! contmue to reap an undiminished harvest from a vtrgm soil. 'fo the geologist, the Gangetic islands, and their migratory colonies, may present an epitome of the globe as t~nanted ~y For during every century we cede some terntory whtch man. · fi the earthquake has sunk, or the volcano has cov~red by 1ts ery . ducts or which the ocean has devoured by Its waves. On pto , h' l . the other hand, we gain possession of new lands, w tc 1 rtvers, tides, or volcanic ejections have formed, or which subterranean causes have upheaved from the deep. Whether the h.uman species will outlast the whole, or a great part of the contmen~ and islands now seen above the waters, is a subject far.beyon . b h h may be mferred the reach of our conJectures ; ut t us muc "' Asiatic Trans., vol. vii. Ch. XII.] TilE PHYSICAl" GEOGRAPHY OF THE GLOBE. ~05 from geological data,-that if such should be its lot, it will be no ~ore than has already fallen to pre-existing species, some of whiCh have, ere now, outlived the form and distribution of land and sea which prevailed at the era of their birth. "\Ve have before shown, when treating of the excavation of new estuaries in Holland by inroads of the ocean, as also of the changes on our own coasts, that although the conversion of sea into l~nd by artificial labours may be great, yet it must always be m subordination to the great movements of the tides and. currents. If, in addition to the assistance obtained by parhamentary grants for defending Dunwich from the waves, all the resources of Europe had been directed to the same end, the existence of that port might possibly have been prolonged for many centuries. But, in the meantime, the cu~r~n.t wo~ld have continued to sweep away portions from the ~dJm~mg chffs on each side, rounding ofF thew hole line of coast ~nto Its present form, until at length the town must have pro~ ecte~ . as a narrow promontory, becoming exposed to the lrrestshble fury of the waves. It is scarcely necessary to observe, that the control which man can exert over the igneous aO'ents is less even than that which he may obtain over th: aquea"us. He cannot modify. the upheaving or depressing force of earthquakes, or the penods or degree of violence of volcanic eruptions ; and on these causes the inequalities of the earth's surface, and, consequently, the shape of the sea and land, appear mainly to depend. The utmost that man can hope to effect in this respect, is occasionally to divert the course of a lava-stream and to prevent the burning matter, for a season at least, from ~verwhelming a city, or other fruit of human industry. No application, perhaps, of human skill and labour tends so g~eatly .to vary th.e state of the habitable surface, as that emp oy.ed m the dramage of lakes and marshes, since not only the statwns of many animals and plants, but the O'eneral climate of. a district, may thus be modified. It is also: kind of alter-ation t o wh I' c h 1· t 1· s d'1f fi cult, I· f not impossible, to find anything |