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Show CAUSES 01r 120 I d ith snow an d I.e f lectino0- the s•u n s rays solid surface covere w ' W'thin the trop1cs, more-for the greater par t of theh year. to1 predom.m ate, t h e s ky Ppose t e ocean b over, where we su d 1 s in the present era; ut l b serene an c ear' a . f would no onger e . ld quick condensatiOns o fl · · ce wou cause . the melting of oatmg 1 d ld deprive the vertical rays d .J' d clou s wou 1 ~ vapour, an 1ogs an . Tl e whole planet, t 1ere1ore, of the sun of half their pow~~· 1 ortion of solar influence, would receive annually a sma er yrc;;, radiation, with some of and the external crust would pail 't d) in it during a different the heat whi.C l 1 d b en accumu a e ' . h 1 1a e . 1 t uld be dissipated mto t e .l' This 1ea wo state of the sunace. 1 which according to the d. o- ur atmosp Jere, ' . . spaces surroun mo 0 . h ve a temperature much mfenor calculations of M. Fourier, a to that of freezing wate:. f 'noctiallands might resem- . · d h hmate o eqm At this perw ' t e c t ne or perhaps be far more f I . nt tempera e zo ' . ble that o t le pi ese l ld tl n inhabit the small Isles and . They who SlOU le d S h wmtery. . tlle Indian ocean an out .l' 1 · 1 are now seen m . . coral ree1s, w uc 1 h h tes of such Jaro-e dimensions Pacific, would wond~\·~ca~nz~~~s? seas; or if, pe~chance, they had once been so pro I . f h a-nut tree or the palm d d frmt o t e coco fo. u. n'fdi tdh eb wotoh awn aters o f some mi· neral spring, or incrus. ted stlici e Y e h ld muse on the revolutwns with calcareous matter, t ey wou d eplaced them by the 'l 'l d ch genera an r that had anm 11 ate su . ' w· 1 ual admiration d the pme 1t 1 eq oak, the chestnut, an k l . f their small lizards with 1 e the s e etons o would t ley comp~r . and crocodiles more than twenty the bones of fossil alligators h 1 d multiplied between h. 1 t former epoc , la feet in length, w IC 1, a a . I'ncluded in an iceberg, · d 1 they saw a pme the tropics ; an w len . 11 tern erate they would drifted from latitudes whiCh :e nc;v ~1 d th~t fore,sts had once be astonished at th<: proof tldubs a or ei·n' their own times but a grown wh ere no thmoo- cou e seen wilderness of snow. d mutations to have taken As we have not yet s~~pose f alnyd d sea in the southern . l . l t've position o an an . . f Place m t 1e Ie a I . . tly the Intensity o . · o-ht still mcrease grea . hemisphere, we ~no 1 d till remaining in the equato:I~1 cold, by transferrm? the a~. ~ outhern latitudes; but It IS and contiguous regwns, to ugb~erts.c ther· as we are too igno- . e the su ~ec 1ar ' unnecessary to pmsu . h d'. t' n of subterranean forces, rant of the laws govermng t e nee 10 CHANGES OF TEMPERATURE. 12l to determine whether such a crisis be within the limits of possibility. At the same time we may observe, that the distribution of land at present is so remarkably irregular, and appears so capricious, if we may so express ourselves, that the two extremes of terrestrial heat and cold are probably separated very widely from each other. The globe may now be equally divided, so that one hemisphere shall be entirely covered with water, with the exception of some promontories and islands, while the other shall contain less water than land; and what is still more extraordinary, on comparing the extratropical lands in the northem and southern hemispheres, the former are found to be to the latter in the proportion of thirteen to one*'' ! 1"'o imagine all the lands, therefore, in high, and all the sea in low latitudes, would scarcely be a more anomalous state of the surface. Let us now turn from the contemplation of the winter of the " great year," and consider the opposite train of circumstances, which would bring on the spring and summer. That some part of the vast ocean which forms the Atlantic and Pacific, should at certain periods occupy entirely one or both of the polar regions, and should extend, interspersed with islands, only to the parallels of 40°, and even 30°, is an event that may be supposed in the highest degree probable, in the course of many great geological revolutions. In order to estimate the degree to which 'the general temperature would then be elevated, we should begin by considering separately the effect of the diminution of certain portions of land, in high northern latitudes, which might cause the sea to be as open in every direction, as it is at present towards the north pole, in the meridian of Spitzbergen. By transferring the same lands to the torrid zone, we might gain farther accessions of heat, and cause the ice towards the south pole to diminish. We might first continue these geographical mutations, until we had produced as mild a climate in high latitudes as exists at those points in the same parallel where the mean annual heat is now greatest. We should then endeavour to calculate what farther alterations would be required to double the amount of change; and the ·great deviation of isothermal lines at present lll Humboldt, on Isothermal Lines. |