CHAPTER 11 



TROPICAL RACES 



The Tropics — -Tropical Races — Primitive man- — Classification — Caucasic 

 division — Ethiopic division — Mongolic division — Amerind division — 

 References. 



THE TROPICS. 



SuPAN suggested that climates should be classified as follows:- — 



1. Tropical or warm climates, extending from the Equator to the 

 mean annual isotherm of 20° C. or 68° F. 



2. Temperate climates, extending from lands possessing a mean 

 annual isotherm of 20° C. or 68° F. to those which have a tem 

 perature of 50° F. for the warmest months of the year. 



3. Cold climates, lying polewards of the isotherm of 50° F. for the 

 warmest months of the year. 



In Fig. I we have depicted the tropical or warm climates as 

 delineated by Supan's lines marked B.B., indicating the mean 

 annual isotherm of 20° C. or 68° F. in north and south latitudes. 

 Both lines are very wavy, the northern being situate about 35 

 degrees north latitude, and the southern at rather less than 30 

 degrees south latitude. This region Supan has divided into two 

 zones, the Tropical Zone Siiid the Subtropical Zone, by lines indicated 

 on Fig. I as A. A., which represent isotherms of 20° C. or 68° F. 

 "for the coldest months of the year in both northern and southern 

 latitudes. 



These lines A. A. correspond more or less to 23J degrees north 

 and south latitude — i.e., more or less to the Tropics of Cancer and 

 Capricorn. 



I. The Tropical Zone. — -Examining the map a little more in 

 detail, it will be noticed that, starting in the extreme west and 

 travelling eastwards, the isotherm both north and south of the 

 Equator is nearly the same as the latitude 23J degrees north or 

 south, but as the coast of iVmerica is reached it dips a little to 

 the south in the Northern Hemisphere, and considerably to the 

 north in the Southern Hemisphere. This variation is caused by 

 cold currents in the sea running along the west coast of America, 

 the more important of which (marked L on the map) is the cold 

 current from the Antarctic. 



Tracing the line farther eastward, it will be noticed that it rises 

 towards the north in the Northern Hemisphere, and falls towards 

 the south in the Southern Hemisphere. In the Northern Hemi- 



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