Waste. 
445 
1883.J 
on the other hand, that when a pound of water at o° C. is 
converted into ice at the same temperature, exactly the 
same amount of heat, previously latent, is liberated, and 
that a balance is thus kept up. This is certainly true ; but 
snow is formed not on the surface of the earth, but high up 
in the air. The heat liberated in its formation is therefore 
emitted into the upper regions of the atmosphere, radiated 
into space, and wasted; 
But snow has further vices in relation to heat. When 
exposed to the diredf adtion of the sun it is very little 
affedbed, hurling back into space, and wasting a very large 
proportion of the incident rays. Hence it has been observed 
to remain unmelted in Ardtic regions, even though the sun 
was powerful enough to soften the pitch in the seams of a 
boat : it melts only where low-tension heat-rays are reflected 
upon it from rocks, walls, and other solid objedfs not buried 
in snow, or, on a larger scale, when warm winds blow from 
some milder region. 
If, on the other hand, snow lies in a country where the 
atmosphere is rich in watery vapour, it condenses the 
moisture into mists and clouds, and thus excludes the rays 
of the sun. Hence snow has been well styled a striking in- 
stance of an effedt which perpetuates and increases its own 
causes. Being produced by the want of heat it extends and 
prolongs that want. The polar snow-caps are fortresses 
antagonistic to life, and which the sun is unable to storm. 
From them issue constantly, season by season, those huge 
masses of icebergs which float down into the temperate, 
and almost into the tropical, seas, and which rank among 
the main causes of cold unfruitful summers in Western 
Europe. We have sometimes thought that if water had 
solidified in deep blue instead of colourless crystals the perils 
of glaciation would have been greatly diminished, as such 
snow would have more readily absorbed the sun’s rays, and 
have in consequence been liquefied. 
The very figure of the earth is doubtless a necessity if the 
planets have been formed by the gradual condensation of a 
fluid or semi-fluid mass whilst revolving upon its axis ; but 
as regards the reception of heat from the sun it is decidedly 
unfortunate. 
If we wish a body to be uniformly heated whilst revolving 
around or before a focus of combustion, we seledt a prolate 
spheroid approaching the shape of a spindle, with its axis 
at right angles to the heat-rays. An oblate spheroid, on the 
contrary, flattened at the poles, receives a much smaller 
share of heat, except at and near its equator. However, if 
