51 PHYSICAL GEOGRAniY OF THE SEA, AND ITS METEOROLOGY. 



of the Obsei-vatory is so arranged that the circulation of the 

 atmosphere through it is led from this basement room, where the 

 pipes are, to all other parts of the building ; and in the process 

 of ihis circulation, the warmth conveyed by the water to the 

 basement is taken thence by the air and distributed over all the 

 rooms. KoAv, to compare small things with great, we have, in 

 the warm waters which are contained in the Gulf of Mexico, 

 just such a heating apparatus for Great Britain, the North 

 Atlantic, and Western Europe. 



151. An anaJocjy slioidng how the Gulf Stream raises temperature 

 in Europe. — The furnace is the torrid zone ; the Mexican Gulf 

 and Caribbean Sea are the caldrons ; the Gulf Stream is the 

 conducting pipe. From the^ Grand Banks of Newfoundland 

 to the shores of Europe is the basement — the hot-air chamber — 

 in which this pipe is flared out so as to present a large cooling 

 surface. Here the circulation of the atmosphere is arranged by 

 nature ; it is from west to east ; consequently 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 temperature of the water-heated air- 

 chamber of the Observatory is about 90°. The maximum 

 temperature of the Gulf Stream is 8G°, or about 9° above the 

 ocean temperature due the latitude. Increasing its latitude 10°, 

 it loses but 2° of tempei'ature ; and, after having run three 

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

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

 the 40th degi-ee 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 Europe the rigours 

 of winter. Moving now more slowly, but dispensing its genial 

 influences 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 immense 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. Depth and temperature. — We know not, except approxi- 

 mately in a few places, what the depth of the under temperature 



