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Show ··.'·· CAUSES OF 112 . d 4~o and in New . , 1 d . latltU e ' . J! d in Van D1eman s an 111 are 1oun . d ·hi'deous paras1tes also 45o The ore Zealand in south lautu o e d 4~o of south latitude *. dvance towards the 38 a~ k on the diffusion of heat a Havino- offered these bnef remar t the surface, we shall now over the ~lobe in the present.s~at.~t~dcs of climate, which must . ceed to speculate on t~e. VlClS.sl h geographical features of pio dl latiOns m t e d ttend those en ess var 1 d . geology. In or er to a r . h temp ate m h ll ou Planet , whiC a.r eh 'c ont he stn. ct 1I' ml' ts of analooo- y' we .s a confine ourselves w1t 111 • • f dry land to sea contmues assume 1st, That the proporthlOn ol me of the land rising above l ' G)dl That t e vo u h ways the same. ~ Y' ntity . and not only t at a · a constant qua ' 'fl' the level of the sea, lS h . ht are only liable to trl mg its mean, but that it~ ~:~r~~:h e:~e ~nean and extreme dep:h variations. Sdly, f e och. and, 4thly, It will of the sea are equal at evt~ry t! ass~me, that the grouping · 'th due cau lOll, t f be consistent, Wl t nt'Inents is a necessary par o too-ether of the 1a n d m. grea . co. ssible that the laws wh I' c h o f t e. for 1t 1s po ' . 1 the economy o na ur ' J! d which act simultaneous y b n 1orces an h govern the su terranea b t' roduce at every epoc 'con-along certain lines, ca?not uth \ the s~bdivision of the whole tinuous mountain-chai~s; so m: be recluded. If it be obland into innumerable Islandfs 1 Yt. npof land and depth of sea jected, that the maxi· mu m o e evath 1e0 gatherino- together of a1 1 are probably not constant, nor erhaps the relative extent the lands in certain parts,l norhe:e~1: arguments which we shall of land and water; we rep y' t : d . f in these peculiarities of adduce will be greatly stre~dgt ebnle a:vlations from the present 1 be cons1 era e . the surface, t Jere 1 11 ther circumstances bemg t1 le same, type. If, for exa~p e, a ~ivided into islands than at another, the land is at one tlme m~re . ht be produced, the mean tern- .~ · t f chmate nng a greater unHorml yo d . f at another era, there were Perature remaining unahlterHe . ; olrayl ~ these when placed in high mountam· s h1'gher than t e lma ' ' . if . s be developed in still higher latitudes~ * These forms of vegetation .mtght perh? f rther from the pole than in the archc. the ice in the antarctic circ~e ~d. no:::t:oun~ainous, temperate, /iumicl, andt ~:! Humboldt observes,. that ~t lS ~~at the family of ferns produces the grea~~e effect parts of th~ equatonal ~:~:ns;herefore, that elevation often co~p;:s:::~les which ber of specles. As we ' 'ly understand that a class o gl . far from of latitude in plants, we may e~I . d zone would flourish on the p ams if nn. grow at a certain height in the o~n thro~ghout the year was equally uu o the equ~tor, provided the tempera w:e . DWfGHT W. TAYLOR CHANGES OF TEMPERATURE. 113 latitudes would cause a greater excess of cold. So if we suppose, that at certain periods no chain of hills in the world rose beyond the height of 10,000 feet, a greater heat might then have prevailed than is compatible with the existence of mountains thrice that elevation. However constant we believe the relative proportion of sea and ]and to continue, we know that there is annually some small variation in their respective geographical positions, and that in every century the land is in some parts raised, and in others depressed. by earthquakes, and so likewise is the bed of the sea. By these and other ceaseless changes, the configuration of the e::trth's surface has been remodelled again and again since it was the habitation of organic beings, and the bed of the ocean has been lifted up to the height of some of the loftiest mountains. The imagination is apt to take alarm, when called upon to admit the formation of such inegularities of the cmst of the earth, after it had become the habitation of living creatures; but if time be allowed, the operation need not subvert the ordinary repose of nature, and the result is insignificant, if we consider how slightly the highest mountain chains cause our globe to differ from a perfect sphere. Chimborazo, although it rises to more than ~1 ,000 feet above the surface of the sea, would only be represented on an artificial globe, of about six feet in diameter, by a gt·ain of sand less than one-twentieth of an inch in thickness :'If.. The superficial inequalities of the earth, then, may be deemed minute in quantity, and theit· distribution at any particular epoch must be regarded in geology as temporary peculiarities, like the height and outline of the cone of Vesuvius in the interval between two eruptions. But, although the unevenness of the surface is so unimportant, in reference to the magnitude of the globe, it is on the position and direction of these small inequalities that the state of the atmosphere and both the local and general climate are mainly dependent. Before we consider the effect which a material chano-e in the distribution of land and sea must occasion, it may b;' well to. remark, how greatly organic life may be affected by those mmor mutations, which_ need not in the least degt·ec alter the Vot. I. * M:o.lte-Bru:1's System of Geography, book i. p. 6. I |
