LIMIT OF PERPETUAL SNOW. 329 



which the snow-capped mountain rises, either solitarilf, or as 

 a portion of a group or chain, and whether this plain may 

 be part of the sea coast, or of the interior of a continent, 

 whether wooded or grassy, of arid sand or rock, or, on the 

 contrary, wet and marshy. 



Under the equator in South America, the height of the 

 snow line is equal to that of the summit of Mount Blanc in 

 Europe, and descends, according to recent measurements, 

 960 French feet (1023 English) lower in the highlands of 

 Mexico, in lat. 19 North; in the southern tropic, on the 

 contrary, in 14-V to 18 S. lat., it ascends, according to 

 Pentland, to an elevation of 2500 French (2665 English) 

 feet above that which it attains under the equator not far 

 from Quito, on Chimborazo, Cotopaxi, and Antisana ; this 

 ascent of the snow line does not take place in the eastern 

 part of the Cordilleras, but in the western and maritime 

 chain of the Andes of Chili. Dr. Gillies affirms that 

 even much farther to the south, on the declivity of the 

 volcano of Peuquenes (lat. 33), he found the snow line 

 reach an elevation of between 2270 T. and 2350 T. 

 (14520 and 15030 English feet). The evaporation of the 

 snow in the excessively dry air of summer and under a 

 doudless sky is so powerful, that the volcano of Aconcagua, 

 north-east of Valparaiso, in S. lat. 32^- (the elevation of 

 which was found by the Expedition of the Beagle to be 

 1400 feet above that of Chimborazo), was once seen free from 

 enow. ( 402 ) In an almost equal northern latitude (30 45 

 to 31) the snow line on the southern declivity of the 

 Himalaya lias an elevation of 12180 French feet (12982 

 English), which is nearly that which might have been con- 

 jecturally assigned to it from many combinations and com- 



