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Show CHANGES OF TilE SURFACE 134 . d h . d larO'e rep tI. 1e s ' -in a wor , .s ue l an water testacea, tortmses, an o or a large river m a 1ot b] ge as the delta of the Ganges, assem a roduce ''ic. climate might be expected to P 1 dge we cannot pretend to In the present sta t eof 0 ur know e th' e climate win·e h pre. · between institute a close companson . . of our secondary forma- . d 1 depos1t10n vailcd durmg the gra ua b 'ferous rocks, for the general tions and that of the older car ~m t both epochs have been so temperature of the surface m~s ad in the same, or perhaps in dissimilar to t h a t no w expefr ience nalogy lose much of tI 1 e1. r . d tl t proofs rom a h any latltu es, 1a f ~ t is required to support t eo. value an d a l arger. body o J.a c s fi'n tense heat d1' mm..1s h , as ' . If the s1gns o . retical concluswns. . of this great series, there . the newer groups 1 . some suppose, m . . . th animal forms of t 1e contl- 1 · d catwns m 0 are neverthe ess m 1 • hich we might consider as tro~ nued prevalence of a chmate w pica! in its character. t" to the phenomena of the turn our atten Ion .. '\Ve may now 1 . l affor d cvi' d enc e of an abrupt transitiOn tertiary strata, w uc 1 . tiler If this remarkable · · f hmate to ano · from one descriptiOn o c f hysical events is merely ap· break in the regular sequence o t p crfect state of our know- P . . f· m the prescn Imp . f . arent, ansmg· 1 to1 t · a clearer pomt o v1ew rve~ to se m . ledge. it nevert le ess se ;:, t chanO'es in the phystcal . . · between grea o the intimate connexwn d 1 ti'ons in the mean tempera-f 1 ·th an revo u geography o. t le cat t:r W c have already shewn that w1l e n ture of the an· and wa . tl n hemisphere was for the . h tt st the nor Jer . the chmate was o e ' d 1. t remains for us to pomt · d by the ocean, an 'I most part occupie. . d'd not become considerable, untl out, that the refngeratwn I s converted into land. a very large porti·O n of that ocean wal d by high mountam. . . · me parts rep ace . nor even until It·a w as m so . . m until these chams h ld each Its maximu . chains. Nor di t e co r d l 1 ds their full extensiOn. attained their full height, an ~ lel an now constructed of A lance at the best geologiCa maps g t' (b~ * f the VI ealden forma wn We do not mean to con~pare the ?xtent. () to that of the Gangetic d~lta, for Weald clay to the Purbeck limestone mclusiVelddition made to the latter IS equa~ we shall afterwards see that the mos.thmWoderln· But J'udging from the great con t N rth nd Sont a es. ' · 1 d charac- ~~~~,~~~I~~~:::::£:si~::, ;~~s ;:~:r EE::~:~~~b:::: we may safely conclude that a co~sl era e permanently supplied by a large nver, AND CLIMATE, CONTEMPORANEOUS. 135 various countries in the northern hemisphere, whether in North America or Europe, will satisfy the inquirer that the greater part of the present land has been raised from the deep, either between the period of the deposition of the chalk and that of the strata termed tertiary, or at subsequent periods, during which, various tertiary groups were formed in succession. For, as the secondary rocks from the lias to the chalk inclusive, are, with a few unimportant exceptions, marine, it follows that every district now occupied by them has been converted into land since they originated. We may prove, by reference to the relative altitudes of the secondary and tertiary groups, and several other circumstances, that a considerable part of the elevation of the older series was accomplished before the newer was formed. The Apennines, for example, as the Italian geologists hinted long before the time of Brocchi, and as that naturalist more clearly demonstrated, rose* several thousand feet above the level of the Mediterranean, before the deposition of the recent Subapennine beds which flank them on either side. What now constitutes the central calcareous chain of the Apennines, must for a long time have been a narrow ridgy peninsula, branching off at its northern extremity from the Alps near Savonna. A line of volcanos afterwards burst out in the sea, parallel to the axis of the older ridge. These igneous vents were extremely numerous, and the ruins of some of their cones and craters (as those in Tuscany, for example) indicate such a continued series of eruptions, almost all subsequent to the deposition of the Subapennine strata, that we cannot wonder at the vast changes in the relative level of land and sea which were produced. However minute the effect of each earthquake which preceded or intervened between such countless eruptions, the aggregate result of their elevating or depressing operation may well be expected to display itself in seas of great depth, and hills of consider-able altitude. Accordingly, the more recent shelly beds, which often contain rounded pebbles derived from the waste of contiguous parts of the older Apennine rocks, have been raised from one to two thousand feet ; but they never attain the loftier • The greater number of Italian naturalists, and Brocchi among the rest, attributed the change of level to the lowering of the Mediterranean; rejecting the.more correct theory of Moro and his followers, that the land had been upheaved. |