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Show 110 DIFI~ERENCE OF CLIMATE IN NORTHERN another reason suggested by Humboldt, to whi~h great weight is due,-the small quantity of land in the tropical and temperate zones south of the line. If Africa and New Holland ex .. tended farther to the south, a diminution of ice would take place in consequence of the radiation of heat from these continents during summer, which would warm the cont ·uous sea and rarefy the air. 'The heated aerial currents would then ascend and flow more rapidly towards the south pole, and moderate the winter. In confirmation of these views, it is stated that the cap of ice, which extends as far as the 68° and 7~ o of south latitude, advances more towards the equator whenever it meets a free sea ; that is, wherever the extremities of the present continents are not o'pposite to it; and this circumstance seems explicable only on the principle above alluded to, of the radiation of heat from the lands so situated. Before the amount of difference between the temperature of the two hemispheres was ascertained, it was referred by astronomers to the acceleration of the earth's motion in its perihelium ; in consequence of which the spring and summer of the southern hemisphere are shorter, by nearly eight days, than those seasons north of the equator. A sensible effect is probably produced by this source of disturbance, but it is quite inadequate to explain the whole phenomenon. It is, however, of importance to the geologist to bear in mind, that in consequence of the procession of the equinoxes the two hemispheres receive alternately, each for a period of upwards of 10,000 years, a greater share of solar light and heat. 'fhis cause may sometimes tend to counterbalance inequalities resulting from other circumstances of a far more influential nature; but, on the other hand, it mnst sometimes tend to increase the extreme of deviation which certain combinations of causes produce at distant epochs. But, whatever may now be the inferiority of heat in the temperate and arctic zones south of the line, it is quite evident that the cold would be far more intense if there happened, instead of open sea, to be tracts of elevated land between the 55th and 70th parallel; for, in Sandwich land, in 54° and 58° of south latitude, the perpetual snow and ice reach to the sea beach; and what is still more astonishing, in the island of Georgia, which is in the 53° south latitude, or the same parallel as the central counties of England, the. perpetual snow descends to the level of the ocean. When AND SOUTIIE• RN IIEMISPIIERES. . we consider this fact d Ill t am. s I.n Scotland d ' an th, en reco 11 ect that the h" h 'd 0 not attrun th J" . 1g est moun Sl e of the equator, we learn the Im~t of perpetual snow on thi~ powerful causes, which d t ~t latitude is one only of g, ions oIf the globe. The peerm e ramn emn e. thfe hcl jmate of parti cu !amra rney- IS p~rt y due to the floating ice ~? ~ t ~snow, in this instance ;~;~:;~•:hth~ vapou~, so that Jnws~~;::l:~ the atmosphere and f· e oggy air. The distan e sun cannot pierce ~~;ttl~aplol~re;:giaonnt~ ~n the oppos~t: !~d~h!~ht~~ebl~rgs .float 1 . . , 1c1pated v , d' .a> me Is as Imlt In t le north l , ' ei y Iuerent. Th . ' ' ( ern 1em1sph e1r extrem north latitude 4~o) t I . h .ere appears to be th A e from Baffin's Bay •' ; w ".c Isles they are sometime: d ~ores been seen, within the las~\ m the other hemisphere theyl~fted Cape of Good H wo years, nt di:ffere t . ave these was two m~pl e, ?etw.een latitude 36o and ~9~otmts off the 0 h 1 es m c1rcumfi • One of t ers rose from ~50 to 300 fi erence, and 150 feet hi h were, therefore of g. t eet above the level of th g +· b , ' Iea volume b I . e sea, and y experiments on the b e ow, smce it is ascert . that for every solid fi uoyancy of ice floating . amed, fi I oot seen ab I m sea-water eet Jelow water§ If . . l ove, t Iere must at lea t b , ' floated f: . Ice Is ands from th s e eight being d:wnarb, thhey might reach Cape Ste ~?rth polar regions , y t e current th . mcent, and tl tic through th e S tra1. ts of G 'b at alwavs sets I' ~ ' len J n 1rom the A tl tIe rranean ' wh ere cI ouds d1 ra.l tar, be drifted m. t o t h e M adn. - t ';,;:rene sky of spring a'::'d s== would immediately def;r~ e great extent of se . er. mates south of the e a gives a particular charact . summers cold Tl qu_ator, the winters being m'ld er to eli-nearly in Iatitu. d tmsR, m Van Dieman's land I ' and the N e o om th . ' correspondi aples, and the sum e, e wmters are more mild th ng whiCh is 7o .tt mers not warme h an at t , . larther from th r t an those at p . JOn Is -ver e equator 11 Th ans, quire abu!.J:O":a~~:~:s;;::,J"rns, for. in~t:~~~: :';,Tc';fe:~ ' a~ equalizatiOn of the • Exam le . seasons, t 0 p s will be given in M , burg, ~y~::e;~s in low Latitude:Ji~ t~:~n:~~e~rthco~ing work on Currents February, Isffo pher to the East India Compru n Hemisphere, by Captain Iios + E . · 1Y ; read to th R • + dm. New Ph ·1 J e oyal Society ~ s J • ourn N 1 coresby's Arctic Re . . o. xv .. p. 193; January 1830 gions, vol, I., P· 234, ' II H. umboldt, ib, |