SNOW-LINE. The snow-line marks that height above the sea-level below which all the snow that falls annually melts during summer; higher than this lies the region of perpetual snow. No general rule for the height of this line call be given. owing to the different causes which may determine it. These are—the situation of the slope in respect of the sun's rays, and hence, other things being equal, it is higher on the s. than on the n. side of mountains; the situation with respect to the rain-bringing winds; the steepness of the slope; and the dryness or humidity of the region. The following are the observed heights of the snow-line in English feet in different parts of the globe: From Int. 0° to 20° it sinks only a very little; from 20° to 70° it continues to fall equably; but from 70° to it sinks with great rapidity. To this general statement Pere are some important exceptions. It is about 4.000 ft. higher on then, than it is on the s. side of the Himalaya, owing to the greater depth of snow that falls on the s. side: to the greater dryness of the climate of Tibet, which increases the evaporation and the heating power 9f the sun's rays; and to the naked rocks and soil of the n. absorbing more heat than
surfaces covered with vegetation. It is higher in the center of continents than near the coasts (the rain being less and the heat greater), as seen on comparing the Pyrenees and Caucasus; and on the e than on the w. coasts of continents, which is strikingly illus trated by liamteltatka (5,240) and Unalashka (3,510), situated respectively on the w. and e. coasts of the 11. Pacific. South of the equator it rises from 0° to 18° very considerably, and more so on the w. than on the e. of the Cordilleras, owing to the small amount of rain and snow which falls on the w. of these mountains. It is as high in 83° s. lat. as in 19' n. lat.; but s. of this it sinks very rapidly, so that in the s. of Chili it is 6,000 ft. lower than in the same latitude in the Rocky mountains, and 3,000 lower than in western Europe. The mean temperature of the snow-line varies much Loin the equator to the pole—from 35° to 20° Fair. In the Alps it is about 25°; and in Norway about 23°.