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Show 108 GULF STREAM. where the mean temperature of the year is that of the coasts of Brittany, the scorching l:eats of summer are.:;rgreatcr than at Cairo and the winters as rigorous as at U psal ... If Jines be drawn round the globe through all those places which have the same winter . temperature, they .are found to d iate from the terrestrial parallels much farther than the li~:s of equal mean annual heat. For the lines of equal inter in Europe are often curved so as to reach parallels of ~titude 9o or 10° distant from each other, whereas the isother-mal lines only differ from 4° to 5o. . Amoncr other influential causes, both of remarkable diver-sity in the mean annual heat, and .of ~nequal division of heat in the different seasons, are the d1rect10n of currents and the accumulation and drifting of ice in high latitudes. That most powerful current, the Gulf stream, after doubling the Cape of Good Hope, flows to the northward along the western coast of Africa, then crosses the Atlantic, and accumulates in the Gulf of Mexico. It then issues through the Straits of Bahama, running northwards at the rate of four miles an h?ur, and retains in the parallel of S8o, nearly one thousand miles fro.m the above strait, a temperature 10° Fahr. warmer than the air. The general climate of Europe is materially affected by the volume of warmer water thus borne northwards, for it maintains an open sea free from ice in the meridian of East Greenland and Spitzbergen, and thus moderates the cold of all the lands lying to the south. Until the .waters .of the ~rea.t current reach the circumpolar sea, the1r specific gravity IS less than that of the lower strata of water; but when they arrive near Spitzbergen, they meet with the water of ~elted.ice whic!I is still lighter, for it is a well known law of tlus flmd, that It passes the point of greatest density when cooled down bcl~w 40° and between that and the freezing point expands agam. 'Ih~ warmer current, therefore, being now the heavier, sinks below the surface, so that in the lower regions it is found to be from 16° to ~Oo Fahrenheit, above the mean temperature of the climate. The movements of the sea, however, cause this under current sometimes to appear at the surface, and greatly to moderate the cold t. ll< On Isothcnnnl Lines. t Scoresby's Arctic Regions, vol. i. p. 210. TEMPERATURE OF THE SOUTHERN IIEMISPIIERE. 109 The great glaciers generated in the valleys of Spitzbergen in the 79° of north latitude, are almost all cut off at the beach' being melted by the feeble remnant of heat retained by the Gulf' stream. In Baffin's Bay, on the contrary, on the east coast of old Greenland, where the temperature of the sea is not miticratcd by the same cause, and where there is no warmer under-cu~ent the glaciers stretch out from the shore, and furnish repeated crops of mountainous masses of ice which float off into the o~ean *. The number and dimensions of these bergs is prodi~ gwus. Capt. Ross saw several of them tocrether in Baffin's Bay d . b agrou~ m wate7 fifteen hundred feet deep! Many of them a:c dnven do~n mto 1-Iudson's Bay, and, accumulating there, diffuse excessive cold over the neiO'hbourincr continent so tl1at c . k' 0 0 ' artm~ F~an lm reports, that at the mouth of Hayes l'ivel', wluch hes m the same latitude as the north of Prussia or the south of Scotland, ice is found every where in digging wells at the depth of four feet ! When we compare the climate of the northern and southern hemispheres, we obtain still more instruction in recrard to the influence of the distribution of land and sea on cli~ate. 'l.'he dry land in the southern hemisphere, is to that of the northern i? the ratio only of one to three, excluding fmm our consideratwn that part which lies between the pole and the 74° of south la~itude, which has hitherto proved inaccessible. The predommance of ice, in the antarctic over the arctic zone is very great; for that which encircles the southern pole extends ·to lower latitudes by ten degrees than that around the nm:th pole T· It is probable that this remarkable difference is partly attributable, as Cook conjectured, to the existence of a considerable tract of high land between the 70th parallel of south latitude and the pole. There is, however, Gl • .S core.s by'.s A rc rl C R eg1· 0n, vo 1. 1· . p. 2 0 8. -D r. Latta's observations on the aciers of Spitzbergen, &c. Edin. New Phil. Journ. vol. iii. p. 97. f Captain Weddell, in 1823, reached 3° farther than Captain Cook and arrived at 74o 15' longitude, 34° 171 west. After having passed through a sea ~trewed with ~umerous i~e-islands, he arrived, in that high latitudt~, a.t an open ocean; but even 1 he had sailed 6° farther south, he would not have penetrated to higher latitudes ~han Captain Parry in the arctic circle, who reached lat. 81° l 01 north. The ~~portant discovery, therefore, of Captain Weddell, does not destroy the presump- 1?n, that the general prevalence of ice, in low latitudes in the southern hemiSJ.Jhere nrls~s from th~ existence of greater tracts of land in the antarctic, than in th; ~rct1c ocean. |