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Show VARIATIONS OF CLIMATE. 124 1. h venth e e.x t' stence in certain influen. ce o f those forces to wh u'lcl oer va1 1 ey, lake or . sea, fm uhs t latitudes of land or water, :d accurate informatiOn o t e be ascr1' b ed · If we p·o sseisns ch.m ate m. the course of twenty t of local fluctuatiOn b dl be considerable. Cer-amoun. s it would often, undou te ty,f Holland and of Eng-centurie ' 1 on the coas o tam. t rac ts ' for examp1 e· , t d Ian d .m the time of the Romans, l d consisted of cu tlVa e hments has at length occu-anh , d al encroac ' · h h w 1. c h the sea ' by gra u. bas b een erwre cted ·' for nell er t e pt. e d . Here an . alteration nor the mean annual 1 different seasons, . d. · 'on of beat m t 1e . h sea is precisely the same lVISl h · vestmg t e . h t of the atmosp ere 111 1 d In those countnes also ea t n the an · . . h as that which res s o nd volcano are in full activity' a ~uc here the earthquake a 'ble variation. The chmate w duce a sens1 d'ffi shorter period may pro. f Malpais in Mexico must 1 er f the once fertile plat.n o 'l d before the middle of the o l t hich prevat e 1 . 1 f materially from t 1a w . ·x mountains, the 1lg lest o ~ ,· ce that time, Sl 1 last century; lOr, :sm above the plateau, have been t ~rown ~P them rising 1700 ~eet I . b the repetition of an mdefimte by volcanic eruptiOns. . t IS d y to volcanic and various other number of local revolutwhns ueof climate is finally brought causes, tl)at a general c ange about. CHAPTER VII!. Geological proofs that the geographical features of the northern hemisphere, at the period of the deposition of the carboniferous strata, were such as would, according to the theory before explained, give rise to an extremely hot climateOrigin of the transition and mountain limestones, coal-sandstones, and coalChange in the physical geography of northern latitudes, between the era of the formation of the carboniferous series and the lias-Character of organic remains, from the lias to the chalk inclusive-State of the surface when these deposits originated-Great accession of land, and elevation of motmtainchains, between the consolidation of tho newer secondary and older tertiary rocks-Consequent refrigeration of climate-Abrupt transition from the organic remains of the secondary to those of the tertiary strata-Maastricht beds-Remarks on the theory of tho diminution of central heat. WE stated, in the sixth chapter, our reasons for concluding that the mean annual temperature of the northern hemisphere was considerably more elevated when the old carboniferous strata were deposited; as also that the climate had been modified more than once since that epoch, and that it approximated by successive changes more and more nearly to that now prevail~ ing in the same latitudes. Further, we endeavoured, in the last chapter, to prove that vicissitudes in climate of no less importance may be expected to recur in future; if it be admitted that causes now active in nature have power, in the lapse of ages, to vary to an unlimited extent the relative position of land and sea. It next remains for ·us to inquire whether the alterations, which the geologist can prove to have actually taken place at former periods, in the geographical features of t?e northern hemisphere, coincide in their nature, and in the time of their occurrence, with such revolutions in climate as would naturally have followed, acc01·ding to the meteoroloo-ical principles already explained. 5 We may select the great carboniferous series, includino- the transition and mountain limestones, and the coal, as the ~dest s!stem .of rocks of which the organic remains furnish any deci~ lv: ev~dence as to climate. We have already insisted on the Indications which they afford of great heat and uniformity of |