METEOROLOGY. 



139 



Snow recently fallen has a bulk ten or twelve times that of 

 the water from which it is formed ; while common ice has a 

 bulk only about one-ninth greater than the water of which it 

 is formed. The temperature of the air in which snow is 

 formed, must be below freezing, that is, 32 Fah. ; and if it 

 falls through a warmer temperature in its descent to the earth, 

 it is melted, hence there is no snow in warm weather, nor in 

 the torrid zone, except on the summits of mountains which 

 reach above the line of perpetual congelation. It may there 

 snow above and rain below. 



The snow line, or line of perpetual snow, varies greatly in 

 altitude, according to location and circumstances. On the 

 Himmalaya chain, according to Humboldt, the snow line on 

 the south side is 4,4000 feet below that on the north side ; so 

 that this line cannot be depended upon as a point by which to 

 estimate the altitude O f mountains. 



[This figure from Muller shows a few of the forms of snow flakes or 

 crystals, all of which belong to the hexagonal system.] 



