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Show 384 ANCIEN'£ AND MODERN LAVAS, archipelago, by earthquakes from the deep, the fundamental and (relatively to all above) the oldest lavas will often be distinguishable from those formed by subsequent eruptions on dry land, by their alternation with beds of sandstone and fragmentary rocks. The supposed want of identity then between the volcanic phenomena of different epochs resolves itself into the marked difference between the operations simultaneously in progress, above and below the water. Such, indeed, is the source, as we stated in our fifth chapter, of many of our strongest theoretical prejudices in geology. No sooner do we studv and endeavour to explain submarine appearances, than we f~el, to use a common expression, out of our element; and unwilling to concede, that our extreme ignorance of processes now continua11y going on can be the cause of our perplexity, we take refuge in a " pre-existent order of nature.'' Throughout a considerable part of Lancerote, the old lavas are covered by a thin stratum of limestone, from an inch to two feet in thickness. It is of a hard stalactitic nature, sometimes oolitic, like the J Llra limestone, and contains fragments of lava and terrestrial shells, chiefly helices and spiral bulimi. Von Buch imagines, that this remarkable superstratum has been produced by the furious north-west storms, which in winter drive the spray of the sea in clouds over the whole island; from whence calcareous particles may be deposited stalactitically. If this explanation be correct, and it seems highly probable, the fact is interesting, as attesting the quantity of matter held in solution by the sea-water, and ready to precipitate itself in the form of solid rock. At the bottom of such a sea, impregnated, as in the neighbourhood of all active volcanos, with mineral matter in solution, lavas must be converted into calcareous amygdaloids, a form in which the igneous rocks so frequently appear in the older European formations. We may mention that recent crevices in the rocks of Trezza, one of the Cyclopian isles at the foot of Etna, are filled with a kind of travertine, as high as the spray of the sea reaches; and in this hard veinstone, fragments, and even entire specimens of recent shells thrown up by the waves, are sometimes included. From the year 1736 to 1815, when Von Duch visited Lan-cerote, there had been no eruption; but, in August, ~89l~, a crater opened near the port of Rescif, and formed, by 1ts CJec- VOLCANOS OF TilE GR r , " ECI.\N AUCIIIPELAGO. 385 twns, in the space of t . ./! y·lo Ie nt earthquakes pl·ec~'e ednetdy -wm· h ours, a considerable hill. and accompanied this eruption* • Grecian A·rchipelago.-l'Ve s to the island of Santorin . h~ll next direct our inquiJ·y of (l I' scuss·m g the merits' asf It wi.l l affor c1 us an opportunity obtai?ed no small share o~ Joa 7,nJ?u1a~· theory, which llas spectmg "craters of elev t' I,, pu ctnty m modern times re-d I ' a IOn, (Erhcbu c ' e sou evement ) as th h ngs ratere, Crateres 1. s Ia n d s of Sant'o rin Tl ey. · ave been t et. me d · The three If ' 1e1 asia and As .. gu almost circular and b ' . . proms1 SUl'l'ound a ' ' a ove SIX miles . d' a1·e chiefly composed of t I . · ltl Iameter. They covered with pumice. b tra~ lytle conglomerates and tufFs · ' u 111 one part f S · ' IS seen to be the fundamental . k ,. , 0 a~torm clay-slate Ioc . I he beds m all these isles No, 15, Chart ani Stell on of s 1 . . c]j • all or"' and"" conliguou• i•land, illl!ot Grecian Artloiptlago. p at a shght angle towards the . lose themselves in the surr d' extcnor of the group, and • oun mg sea ; whereas, on the con- . Ferussac, Bulletin des S . shU burning when th Cl. Nat., tome V., p. 45.-1825 The volcano was VoL, I. e accotmt here cited was written. . 2 c |