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Show 306 EOCENE PERIOD· [Ch.XXII. bury, m. Berk sh 't re, t.s a b ou t five miles long an. d two in breadth. The upper an d l ower cl 1 a lk , as will be seen. m. the acc.o mpa. ny. I.n cr sect1· 0n ........ , an d th e upper green-sand dtp m ophp ohsi te d'tdre c- • 0 ttons from an an t't c linal axis which passes throug t e m1 dle of the va1 1 ey a l ong the line a ' b' of the ground-pl. an (No. 78). We subjoin an additional wood-cut, as conveymg a scale of N. No. 80. S. I __ , Yalley of Kingsclere. het· gh ts more near ly approaching to th.a t of nature, although the a1 u ·t u d es, m· proportion to the horizontal ex.t ent, are even m· t h'1 s, perh aps, s omewhat in excess. On each .s tde .o f .t he val· ley we find escarpments of chalk, the strata of whiCh dtp moppo· s·i te d't ree tt' ons, , 1·n the northern escarpment to the north, and m· t 11 e sou th ern to tl1e south · At the eastern and western ex- trem1·t 1· es o f th e va lley ' the two escarpments become confluent, prect·s e1 y m· tl1 e same manner as do those of the .N o.r th and Sout1 1 D owns, a t the eastern end of the '¥e ald d1stnct, near P eters fi el d . A n d as ' a few miles east of the town last men· tt.o ne d ( see Map, plate V·) • the firestone, or upper green-sand, is laid open in the sharp angle between the escarpment of the Alton Hills and the western termination of the S~uth.Downst; so m. t h eva1 1 ey of Kincor sclere the same formatiOn IS seen to crop out from beneath the chalk. . ' The reader might imagine, on regardmg ?r .. Buckland s sect.t on (N o. 79) ' where ' for the sake of eluctdatmg th.e geo-locrical phenomena, the heights are greatly exagg~rated m pr~- ortion to the horizontal extent, that the solutiOn of contl· pot'ty of the strata bounding the valley of Kingsclere had been n.u 1 due to elevation and fracture, unasst·s t ed b y aqu. eou.s s1mp Y 1 (N 80) 1t w1ll ca.u ses; btlt by reference to the true sea e o. ' * Copied by permission from Dr. Bucklan d' sp1a t e XVII ., Geol. Trans., 2nd Series, vol. ii. . . t See Mr. Murchison's map, plate XIV.,lbld. Ch. XXII.] l'ROOl<'S OF DENUDA1'fON. 307 immediately appear, that a considerable mass of chalk must have been removed by denudation. . If the anticlinal dip had been confined to the valley of Kingsclere, we might have supposed that the upheaving force had acted on a mere point, forcing upwards the superincumbent strata into a small dome-shaped eminence, the crown of which had been subsequently cut oft: But Dr. Buckland traced the line of opposite dip far beyond the confluence of the chalk escarpments, and found that it was prolonged in a more northwest direction far beyond the point a, diagram No. 78. In following the line thus extended, the strata are seen in numerous chalk-pits to have an opposite dip on either side of a central axis, from which we may clearly infer the linear direction of the movement. Perhaps the intensity of the disturbing force was greatest where the denudation of the valley of lGngsclere took place; but this cannot be confidently inferred, for the quantity of matter removed by aqueous agency must depend on the set of the tides and currents at the period of emergence, and not solely on the amount of elevation and derangement of the strata. Many of the valleys enumerated by Dr. Buckland as having a similar conformation to that of Kingsclere, run east and west, like the anticlinal ridge of the Weald valley. Several of these occur in Wiltshire and Dorsetshire, and they are all circumscribed by an escarpment whose component strata dip outwards from an anticlinal line running along the central axis of the valley. One of these, distant about seven miles to the north-east of Weymouth, is nearly el1iptical in shape, and in size does not much exceed that of the Coliseum at Rome. Their drain acre b is generally effected by an aperture in one of their lateral escarp-ments, and not at either extremity of their longer axis, as would have happened had they been simply excavated by the sweeping force of rapid water*. 'It will be seen,' continues Dr. Buckland, 'if we follow on Mr. Greenough's map the south-western escarpment of the • Dr. BucklandJ Geol. Trans., 2nd Series, vol. li. p 122. X2 |