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Show lUi •' HURS'l'ING OV A tAl< E beneath drift-wood and mountain-ruins if~.. It is almost super• fluous to point out to the reader that the lower alluvial plains are most exposed to such violent floods, and are at the same time best fitted for the sustenance of herbivorous animals. If, therefore, any organic remains are found amidst the superficial heaps of transported matter, resulting from those catastrophes, at whatever periods they may have happened, and whatever may have been the former configuration and relative levels of the country, we may expect the imbedded fossil relics to be principally referrible to thiA class of mammalia. But these catastrophes are insignificant, when compared to those which are occasioned by earthquakes, when the boundary hills, for miles in length, are thrown down into the hollow of a valley. We shall have an opportunity of alluding to inundations of this kind when treating of earthquakes, and shall con .. tent ourselves at present with selecting an example, of modern date, of a flood caused by the bursting of a lake; the facts having been described, with more than usual accuracy, by sci-entific observers. Flood in the Valley of Bagnes, 18l8.-The valley of Bagnes is one of the largest of the lateral embranchments of the main valley of the Rhone, above the Lake of Geneva. Its upper portion was, in 1818, converted into a lake by the damming up of a narrow pass, in consequence of the fall of avalanches of snow and ice, precipitated from an elevated glacier into the bed of the river Dranse. In the winter season, during continued frost, scarcely any water flows in the bed of this river to preserve an open channel, so that the ice-barrier remained entire until the melting of the snows in spring, when a l~ke was formed above, about half a league in length, wh1ch finally attained a depth of about two hundred feet in parts, and a width of about seven hundred feet. To prevent or ]essen the mischief apprehended from the sudden bursting of the barrier, an artificial gallery, seven hundred feet in length, was cut through the ice, before the waters had risen to a great height. When at length they accumulated and flowed through 111 Silliman's Journal of Science, vo1. xv., No.2, p. 216, Jan. 1829. tN TilE VAlLEY Ol<' BAGNES. 195 this tunnel, they dissolv d h . channel, until nearly hal~ o: ~h Ice, and thus deepened their were slowly drained off. B e whole contents of the lake f h h · ut, at length h o t e ot season the I . ' on t e approach f . ' centra portiO f h ma~s o Ice gave way with a n ° t e remaining residue of the lake was empt' d . tlremendous crash, and the f o I·t s d escent, the waters e Ie m 1alf an h our. I n the course d ncountered s 1 an at each of these the . evera narrow gorges b . Y 1 ose to a great h · h • urst, With new violence I. t h eJg t, and then I ' n o t e next b · . roc {S, forests, lwuses brida d . asm' sweepmg alona ' oes, an cult1vat d 1 d 0 g~eater part of its course th n d e an · For the k 0 noo resembled · roc and mud ' rather tl Jan o f water S nf movmg mass of mary rock, of enormous m . . orne ragments of pri-dimensions, might be com a adgm~ulde, and which, from their P re Wit 10ut exag . · were torn out of a m . get atton to houses .r ore ancient alJ · d ' Jor a quarter of a mil Th .uvlon, an borne down tl . e. e velocity of th . rst part of Its course was th' t h e water, 111 the dI.m ·lm ·s hed to six feet 'b I! •I r y-t ree ~e e t per second which h . elore It reached th L k ' w ere It arrived in si'x I d e a e of Geneva .r · 1ours an a h If h . ' wrty-five miles* • 'l'h.IS n d l a ' t e distance being HOO eft b h. d . Martigny' thousands of t e m It, on the plains of' · h rees torn up b I Wit the ruins of build' "' y t le roots, together town were :6lled with mdgs. ~orne of' the houses in that expand·m g in the plain omf uM up. to th e secon d story. After did no further damage. but artlgny, i~ entered the Rhone, and drowned above Marti' some bodxes of men, who 1Jad been tance of about thirt ~~ny, flwer~ afterwards found at the d' L k y rni es, oatma I f Is-a c of Geneva, ncar Veve o on t.le urther side of the are recorded to h ave occurredY · t I~n undatiOn.s , precisely si· mi'1 ar and fl'om the same cause. In al5;~m;r perwds in this district: a~d the waters, descendina witl ? • or. e~amp1e, a lake burst, t e. thown of Martigny, where frlollre~JStib1e fury, destroyed dpe nds ed · I n a s.u m. lar flood fift m sixty to eJ· g h ty persons re and forty persons 'd y years before, one llun-aftIe r th. e d eb a"c le of 1818w ethree Dr owned . F. m. several months :; ,tlshJfted its position ~ontinu~~ns;., havmg ~o settled chan-le valley, carryina y rom one side to the other . * o away newly-erected brid See ges, under-an account of th . Journ vol · e mnnuatiou of the v 1 u lion, &c , t., P• 187, Drawu up from thtl ~ e .Bagnes, in 1818, in Ed. Phil , emoir o~ M. Escher, with a Iitle~ 02 |
