CLASSIFICATION OF CLIMATES. 693 



For the sake of convenient reference, I shall 

 regard the earth as divided into five zones or 

 isothermal bands, each of which presents a differ- 

 ent climate. For example, whenever the mean 

 annual temperature is 80 or upwards, and sum- 

 mer perpetual, the climate is hot or tropical. Ac- 

 cording to Humboldt, the mean of the year varies 

 from 80 to 60, between lat. 30 in North Africa, 

 and 43 in Europe ; and from lat. 23 to about 33 

 N. in Asia and America. In this zone, summer 

 greatly predominates over all the other seasons, 

 and the climate may be denominated warm. But 

 in the middle latitudes, where the duration of sum- 

 mer, autumn, winter, and spring, is nearly equal, 

 and the mean temperature of the year varies from 

 60 to 50, as in the greater part of Europe, nor- 

 thern Persia, China, and most of the United 

 States, the climate should be designated as tern- 

 perate. Where the mean of the year ranges from 

 50 to 40, and winter predominates over any of 

 the other seasons, as in central Asia, Russia, Nor- 

 way, Sweden, Denmark, and Poland, in Europe ; 

 and Canada, Nova Scotia, New Brunswick, and 

 the northern portions of the United States in 

 America ; the climate should be distinguished as 

 cold. But in all the desolate regions beyond, in 

 which the mean annual temperature varies from 

 40 to 32, or even ; and where winter continues 

 from nine to ten, and even eleven months in a few 

 places, the climate should be termed frigid. 



