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Show 80 NEWER I'LIOCEN E pERIOD· [Ch. VII, . . of the basalt is confirmed by the This theory of the mtruston 1 been O'reatly altered, and . 1 es the clay 1aS o fact, that m some P ac d occasionally contorted in d d b tl action of heat, an . har ene Y 1e tl e lamination not havmg been t. rdinary manner, 1 the most ex rao . rendered much more con-oblitet ·ated, but, on the contrary, . b the induratinO' process. sptcuous Y d to(No l5) is a careful representation The annexed woo -cu r • f ortt.o n of t l1 e a1 t er.e d rock ' a few feet square, where the 0 a P . . f nd and clay have put on the appearalternate tlun lammre o sa d . ance win.c h we of ten ob se rve in some of the most contorte of the primary schists· No. 15, Contortions in the newer Pliocene strata, Isle of Cyclopa. A great fissure, running from east to. w~st, nearly divides the island into two parts, and lays open 1ts 1~ternal structure. In the section thus exhibited, a dike of lava Is seen, fh~st cut· ting through an oldet· mass of lava, and th~n penetratmg th.e superm. cu mbent tertiary strata• In one locahty, the lava ·r amh t· fies and terminates in thin veins, from a few feet to a few me es in thickness (see diagram No. 16). Ch. VII.] CYCLOPIAN ISLES, No. 16. a b c a b Newer Pliocene strata invaded by lava, Isle of Cyclops (!tot-iz onlalaeclion). a, Lava. b, laminated clay anu sand. c, the same altere<l. 81 The at·enaccous laminre are much haedened at the point of con· f tact, and the clays are converted into siliceous schist. In this island the altered rocks assume a honeycombed structure on their weathered surface, singularly contrasted with the smooth and even outline which the same beds present in their usual soft and yielding state. 'l'he pores of the lava are sometimes coated, or entirely filled, with carbonate of lime, and with a zeolite resembling analcime, which has been called cyclopite. The latter mineral has also been found in small fissures traversing the altered marl, showing that the same cause which introduced the minerals into the cavities of the lava, whethet· we suppose sublimation or aqueous infiltration, conveyed it also into the open rents of the contiguous sedimentary strata. Lavas of the Cyclopian Isles not cu·rrents from Etna.-The phenomena of the Bay of Trezza are very important, for it is evident that the submarine lavas were produced by eruptions on the spot, an inference which follows not only fmm the presence of dikes and veins, but from those tuff's above CasteUo d'Aci, which contain angular fragments of hardened marl, evidently thrown up, together with the sand and sc01·ire, by volcanic VoL, III. G |