Democratic Sentinel, Volume 5, Number 22, Rensselaer, Jasper County, 8 July 1881 — An Explanation. [ARTICLE]

An Explanation.

The reason why snow at great elevations does not melt, but remains permanent, is owing to the fact that the heat received from the sun is thrown off into the stellar space so rapidly by radiation and reflection, that the sun fails to raise the temperature of the snow to the melting point. The snow evaporates, but it does not melt. The summits of the Himalayas, for instance, must receive more than ten times the amount of heat necessary to melt all the snow that falls on them, notwithstanding which the snow is not melted. And in spite of the strength of the sun and the dryness of the air of those altitudes, evaporation is sufficient to remove the snow. At low elevations, where the snowfall is probably greater, and the amount of heat even less than at the summits, the snow melts and disappears. This we must attribute to the influence of aqueous vapor. At high elevations the air is dry, and allows the heat radiated from the snow to pass into space ; but at low elevations a very considerable portion of the heat radiated from the snow is absorbed in passing through the atmosphere. A considerable portion of the heat thus absorbed by the vapor is radiated back on the snow ; but the heat thus radiated, being of the same quality as that which the snow itself radiates, is on this account absorbed by the snow. Little or none of it is reflected, like that received from the siui. The consequence is, that the heat thus absorbed accumulates in the snow till melting takes place. Were the aqueous vapor possessed by the atmosphere sufficiently diminished, perpetual snow would cover our globe down to the seashore. It is true that the air is warmer at the lower level than at the higher level, and by contact with the snow must tend to melt it wore at the former than at the latter position. But we must remember that the air is warmer mainly in consequence of the influence of aqueous vapor, and that were the quantity of vapor reduced to the amount in question, the difference of temperature at the two positions would not be great.