388 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1908. 
THE ANDES MOUNTAIN REGION. 
The distinction between the coast and the sierra has already been 
explained. [The division line between the sierra and the Amazon 
region would seem to be simple enough if it is based on the presence 
of the forest, as is implied when the word “ montafia” is used. (See 
p. 886 above.)] The tree line, however, especially in the northern 
part of Peru, according to the data which the writer has obtained 
from reading, rises well up onto the flanks of the Andes, and indeed 
covers some of the mountains which may be appropriately classed 
with the Andes region. It may also be noted that the limits of the 
forest have never been accurately shown on any map. It would seem 
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Fig. 1.—Variations of temperature at Lima. 
proper to restrict the Amazon region to the plains lying to the east 
of the mountains in order to make the division a physiographic one. 
It is not possible to draw this line from information now available. 
In the accompanying sketch map of the Cordillera of the Andes the 
hachuring of the mountainous area has been done as accurately as 
possible from available data, but it will be remembered that Rai- 
mondi’s map of Peru, which is the most detailed, is known to be de- 
fective, and to a considerable extent the hachuring on it is imaginary. 
Divisions of the Andes region. 
The main features of the Andes are the Cordilleras proper, which 
will be described in some detail later. Corresponding with them 
