52 PHYSICAL GEOGE.iPHY OF THE SEA, AND ITS METEOROLOGY. 



atmosptiere is arranged by nature ; it is from west to east ; conse- 

 quently it is such that the warmth thus conveyed into this warm- 

 air chamber of mid-ocean is taken up by the genial west winds, 

 and dispensed, in the most benign manner, throughout Great 

 Britain and the west of Europe. The mean temperatm-e of the 

 water-heated air-chamber of the Observatory is about 90"^. The 

 maximum temperature of the Gulf Stream is 86°, or about 9° 

 above the ocean temperatm-e due the latitude. Increasing its 

 latitude 10°, it loses but 2° of temperature; and, after having rmi 

 three thousand miles towards the north, it still preserves, even in 

 winter, the heat of summer. With this temperature it crosses 

 the 40th degree of north latitude, and there, overflowing its liquid 

 banks, it spreads itself out for thousands of square leagues over 

 the cold waters around, covering the ocean with a mantle of 

 warmth that serves so much to mitigate in Em'ope the rigoiu'S of 

 winter. Moving now more slowly, but dispensing its genial in- 

 fluences more freely, it finally meets the British Islands. By these 

 it is divided (Plate IX.), one part going into the polar basin of 

 Spitzbergen, the other entering the Bay of Biscay, but each with a 

 warmth considerably above the ocean temperature. Such an im- 

 mense volume of heated water cannot fail to carry with it beyond 

 the seas a mild and moist atmosphere. And this it is which so 

 much softens climate there. 



152. We know not, except approximately in a few places, 

 Depth and tempera- wdiat the depth of the Under temperatm'e of the 

 t""^^- GuLf Stream may be ; but assuming the temperature 

 and velocity at the depth of two hundi'ed fathoms to be those of 

 the surface, and taldng the well-kno"^^i difference between the 

 capacity of air and of water for specific heat as the argument, a 

 simple calculation mil show that the quantity of heat discharged 

 over the Atlantic fi'om the waters of the Gulf Stream in a winter's 

 day would be sufiicient to raise the whole column of atmosphere 

 that rests upon France and the British Islands from the freezing- 

 point to summer heat. 



153. Eveiy west A^ind that blows crosses this stream on its way 

 Contrasts of climates to Em'opo, and carrics with it a portion of this heat 

 tudes! ^^™^ ^ to temper there the northern mnds of winter. It 

 is the influence of this stream upon climate that makes Erin the 

 *' Emerald Isle of the Sea," — that clothes the shores of xAlbion 

 in evergreen robes, while in the same latitude, on this side, the 

 coasts of Labrador are fast bound in fetters of ice. In a valuable 



