192 . PHYSICS, 
Mountsin Chains. Latitude. Elevation. | 
Cordilleras of Quito 0°— 12°S. 15,730 : 
. Bolivia 16 —172 S. 17,060 
a Mexico 19 N. 15,0380 
Northern side 16,940 
Himalaya Southern side 31 12,470 
Pyrenees _ 48 8,950 
Caucasus 43 10,870. 
Swiss Alps 46 8,760 
Carpathians 49 8,500 
Altai 50 6,395 
F ( Interior 70 3,512 
| Norway ( Coast 714 2,302 
In illustration of the subject let the reader refer to pl. 28, fig. 2, where 
NESQ is the earth’s surface, CDEF the outer boundary of the atmosphere, 
ANBS a section of the limit of perpetual snow, which, apart from single 
irregularities, attains its greatest height, AE and BQ, in the equatorial 
regions, coming down to the surface of the earth near the poles. It isa 
great error to suppose that the snow line always lies in those regions where 
the mean annual temperature is 32° F.; it almost always‘lies higher than 
this. Its altitude depends principally upon the temperature of the hottest 
month, and also upon the local moisture, the shape of the mountains, &c., 
and is far from increasing regularly towards the equator. Hence it not 
rarely occurs that the snow line is higher on one mountain than on another 
which lies nearer the equator. Thus in Norway this line lies proportionably 
very high, being 400 feet higher at a latitude of 70° than in the islands 5° 
further south. As a general rule the snow line lies lower on the coast of a 
country than in its interior. Under the equator the snow line of South 
America reaches the height of Mont Blanc; fourteen to eighteen degrees 
south of the equator in the Chilian Andes, according to Pentland, it rises 
2500 feet higher than under the equator, as at Quito, Chimborazo, Cotopaxi, 
and Antisana. The reason of the lesser height of the snow line on the 
north side of the Himalaya than on the south (see preceding table) is to be 
found in the deposit of immense quantities of rain and snow on the south 
side, from the atmosphere charged with the vapors of the Indian Ocean, far 
less falling from the dry air of the northern declivity. Even in the Alps 
there is a great difference in this respect between the south and north sides. 
Saussure observed that the great fields of snow in the Alps were capable 
of depressing the snow line by as much as 600 feet. In some cases 
these curves in the snow line are very numerous, as shown in 
pl. 23, fig. 3. 
While we have a means of examining the lower snow line, owing to its 
accessibility, we have none for the upper limit, because the mountains of 
the earth do not lift themselves into those regions where, on account of the 
too great rarity and dryness of the air, snow no longer presents itself... The 
term upper snow line, as used by some authors, is not to be understood in 
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