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Show CHANGES 01•' TilE SURFACE 138 · . The granitic axis f . condary series. . the newer members o o~n se . h as a ridge formed by manne f that chain does not nse s.o htg . f which shew thern to oca lcareous beds, t 1J e orgamc remha mlks oo r a formati.O n of ab out . 1 t f our lower c a ' . h . be the equtva en s o . t tl e base of tlus great c am that age fir.. The tertiary strataha 1 and retain a horizontal . 1 . d above t e sea, 1 . h are only slight y raise . f f the disturbances to w 11c Position, without partakmg ob_anyt do so that the great barrier the older sen.e s 1l as been .s u ~ec e 1' ost entirely upheave d m. d Spam was am d between France an d 't' n of the secondary an the eposi Io f the interval between 1 owe the greatest part o tertiary strata t . .T he Jurbat,e rara snoe, an convulsions wh "I Ch h ap ... their present elevatiO~ .to suf t ·n tertiary groups; at which 1 d position o cer at . b h pened after t 1~ e "ch had been previously raised a ove t e time that portiOn w hi ntire alteration of form t. In level of the sea under~ent an ~ France and England, where other parts of the contbme~lt, as mounded by gently-rising hills, l r in asms surr the newer 'rdo c <s Jteh at consi. d erab le spaces were redeemed from we find. e· v1 1 enceea n an d conver t ed into dry land after th.e chaIl k the ongma oc l · · of the tertiary deposits. n was formed' and beforedt 1e orttgttna were not raised into lofty the secon ary s ra b these ca· sesh, . ns h.k e 1 Al Apennines and Pyrenees, ut t 1e ps, ' . · mountam c at ' clear of their partial conversiOn mto the proofs are not les~ . The chalk for example, must land anterior to the tertJar~ erla. c m of sedi:nent from tranquil . · d · the sea m t 1e 10r have orJgmate m . . lrs of the Paris and London b b I! ·e the terttary Ioc ~ · d water ; ut e 1 m . f 't had been so raise d · d large port1ons o I basins were eposite ' d t . power of the elements. b d to the es roymg . as to e expfo fsle. t had b een was 11 e d out by torrents and rivers The layers o 111 . matri•x roun d ed b Y attrition ' and trans. .. from their cretaceous ' tt ched themselves, and m ported to the sea, where oyst~rs a ~il covered by other beds some localities grew to a ful~~e: un er derivative deposits of flint-pebbles or sand. hes~ n~w s and in the inferior are found abund~ntly alo~g t e d ~~leer ~re often interstratistrata of our tertlary basm~,. a~ . £ ! that the various trees fied with lignite. We may .lair y m ei, . * This observation, first made by M . Boue ' has been since confirmed by M. D. utf rSeneoe ya. Memoir Ly M. Eh.e de-B eaumont ' Ann' . des Sci. Nat., Nov. 1829, P· 286. t M. Elie de Beaumont, ibid., Dec. 1829, P· 346. AND CLIMATE, CONTEMPORANEOUS. 139 and plants which enter into the composition of this lignite, grew on the surface of the same chalk which was then wasting away and affording to the torrents a constant supply of flint gravel. We cannot dwell longer on the distinct periods when the secondary and various tertiary groups were upraised, without anticipating details which belong to other parts of this treatise; but we may observe, that although geologists have neglected to point out the relation of changes in the configuration of the earth's surface with fluctuations in general temperature, they do not dispute the fact, that the sea covered the regions where a great part of the land in Europe is now placed, until after the period when the newer groups of secondary rocks were formed. There is, therefore, confessedly a marked coincidence in point of time between the greatest alteration in climate and the principal revolution in the physical geography of the northern hemisphere: It is very probable that the abruptness of the transition from the organic remains of the secondary to those of the tertiary epoch, may not be wholly ascribable to the present deficiency of our information. We shall doubtless hereafter discover many intermediate gradations, (and one of these may be recognized in the calcareous beds of Maestricht,) by which a passage was effected from one state of things to ano ... ther; but it is not impossible that the interval between the chalk and tertiary formations constituted an era in the earth's history, when the passage from one class of organic beings to another was, comparatively speaking, rapid. For if the doctrines explained by us in regard to vicissitudes of temperature are sound, it will follow that changes of equal magnitude in the geographical features of the globe, may at different periods produce very unequal effects on climate, and, so far as the existence of certain animals and plants depends on climate, the duration ·of species may often be shortened or protracted, according to the rate at which the change in temperature proceeded; Let us suppose that the laws which regulate the subterranean forces are constant and uniform, (which we are entitled to assume, until some convincing proofs can be adduced to the contrary;) we may then infer, that a given amount of alteration in the superficial inequalities of the surface of the planet ~lways requires for its consummation nearly equal periods of time, Let us then imagine the quantity of land between |