484 



PHYSICAL GEOGRAPHY. 



CHAPTER XV. 



PHYSICAL CLIMATE. 



E use the word climate to denote the 

 temperature of the air in various regions 

 of the globe an all-powerful cause in 

 the determination of their physical as- 

 pect. Great diversities meet us here, 

 from the extreme of cold, which pro- 

 duces perpetual congelation towards the 

 poles, where no vegetable life is found, 

 to the fervid heat of an equatorial dis- 

 trict, under the action of which, in con- 

 nection with the prevailing moisture, 

 vegetation attains its greatest luxuri- 

 ance. It has been remarked that it is 

 easy to conceive of an astronomical ar- 

 rangement, according to which all parts 

 of the earth would have had the same, 



or nearly the same, climate. But, had this been the case, our planet, though full of 

 life, would not have been furnished with that useful and agreeable variety of vegetable 

 productions and animal forms which it now presents, and many articles of convenience 

 and luxury which the existing arrangement affords to the human race would have been 

 wanting. It is an instance of wise and benign adaptation that the human frame has been 

 so constituted as to be able to bear the striking diversities of climate which distinguish 

 the abode of mankind, both the heat of the burning plains of Beloochistan, and the cold 

 of the icy shores of Greenland. It has been" proved by experiment that the body is 

 capable of enduring very great extremes of temperature, and sudden changes of it, without 

 being seriously affected. Dr. Fordyce exposed himself to an atmosphere raised to the 

 temperature of 200 of Fahrenheit, or nearly to the boiling point of water, for ten 

 minutes, and a thermometer fixed under his tongue indicated only 98, so that his body 

 resisted the impression of the artificial heat, and retained nearly its .natural temperature, 

 which the surrounding air exceeded by more than 100. On the other hand, a degree of 

 cold which depressed the mercury in a thermometer 52 below the freezing point, has 

 been borne with only a slight addition to the ordinary clothing. Owing to this capacity 

 of the frame, man can accommodate himself to the circumstances of the earth he inhabits, 

 live amid the perpetual ices of the north, or under the fierceness of a torrid climate, and 

 pass without difficulty from the one to the other, for the purposes of commerce and 

 enterprise. Though many members of the vegetable kingdom show a marked indifference to 

 change of temperature, and hence are transportable with success from cold to heat, or from 

 heat to cold ; yet vast numbers exhibit as marked an incapacity for the transition. The 

 cinnamon bushes that clothe the surface of Ceylon would not endure a removal to the bleak 

 moors of England, nor our highland pines a transplantation to the level plains of Hindo- 

 stan ; but the different members of the human family, in varying degrees, display a physical 

 adaptation for emigration into any of the habitable parts of the earth, however discordant 

 their temperature, the frost biting in one region, the fire-king breathing in another. 



We proceed to mention the causes which determine physical climate, and induce its 

 differences : 



