108 PHYSICAL GEOGRAPHY. 



mode of reckoning is continued to the Polar Circles 

 where the longest day is -24 hours, and is consequently 

 considered to be in the 24th climate. Between the Polar 

 Circles and the Poles the reckoning is carried on by 

 months ; so that those places which are contained between 

 the Polar Circles, and that parallel where the sun keeps 

 above the horizon for one month, will be in the 25th 

 climate, for two months in the 26th climate ; and so on 

 to the Poles, which will be in the 30th climate. 



The other principal cause for alteration in the tempe- 

 rature is the height of the place above the level of the 

 sea ; even in the Torrid Zone elevated lands have their 

 temperature lowered in proportion to such elevation. 

 An elevation of from 6,000 to 8,000 feet will render the 

 temperature as mild as that of the Temperate Zones : 

 Mexico has nearly such elevation, and Quito somewhat 

 greater, both of which are remarkable for the mildness 

 of their temperature. In Asia also the elevated tro- 

 pical lands have a temperature particularly mild and sa- 

 lubrious. 



Independent of the causes already named, mountains 

 have a surprising effect on the temperature of a country, 

 occasionally acting as barriers to the hot winds of one 

 country and the cold winds of another. Siberia, for 

 instance, being exposed to the piercing winds from the 

 Frozen Ocean, and shut out by the Altaian mountains 

 from the warm winds of the southern regions, has a 

 much lower temperature than under other circum- 

 stances it might have. At Naples the Tramontanes, as 

 they are called, coming from the frozen regions of 

 the Alps and Apennines, are intensely cold ; while 

 the Siroccos, or southern winds, are as excessively hot. 

 Even in our own country, the mildness of the tempe- 

 rature at many parts of the southern coast is well known, 

 being shielded by hills from the northerly and easterly 

 winds. 



The cultivation of a country, and the nature of its 

 soil, have also an effect on the temperature. Forests 

 and profuse vegetation of all kinds imbibe the sun's 

 rays without reflecting them, and consequently lower 

 the temperature, which is one reason why those parts of 

 North America that lie within the same parallel as Eng- 



