NOTE ON THE MAP OF SOUTH AMERICA. 



In the annexed map an attempt has been made to represent the 

 probable course of the isothermal lines — lines denoting equal 

 temperature — in the South American continent. The black 

 lines indicate the mean temperature for the entire year ; the red 

 lines that for January, the hottest month ; and the green lines 

 that of July, the coldest month. The numbers placed over 

 each line in corresponding colours indicate the temperature in 

 degrees of the Centigrade scale. We possess a fair amount of 

 information as to the meteorology of the coasts of the continent ; 

 but of the interior our knowledge is miserably deficient, and is 

 nearly limited to several stations in Argentaria, and a few in the 

 basin of the Amazons. As a result, the course of the isothermal 

 lines in the interior is to a great extent conjectural. As in all 

 similar maps, no account has been taken of the relief of the 

 surface ; when a line crosses a mountain range, the tempera- 

 ture indicated is that which would be found, as is assumed, 

 if the height were reduced to the sea-level. No attempt has 

 been made to show the variations of temperature with the 

 season in the part of the continent near the equator. These 

 are very slight, and depend mainly on local conditions, the 

 mean temperature of the year varying from 25-5° to 28° C, or 

 from about 78° to 82° Fahr. ; the hottest seasons near the 

 equator, apart from local conditions, being those of the equinoxes. 

 The chief interest of the map to the physical geographer 

 arises from the remarkable effect of the southern, or Humboldt, 

 current, in lowering the temperature of the western coast between 

 the fifth and the fortieth degrees of south latitude. This is,, of 



