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POPULAR SCIENCE REVIEW. 
vapours add themselves to that mantle of snow which for ever 
enwraps the higher mountain peaks ? Up to a certain point 
the summers heat annually removes the winter's snow, — the 
gain on the one hand and the loss on the other are evenly 
balanced ; but beyond this point, as we rise into colder 
regions, the gain exceeds the loss, and a residuum of unmelted 
snow is added to the yearly fall. We have passed the so-called 
snow-line , above which increasing quantities of snow would, in 
this way, yearly accumulate. Let this action continue unchecked 
for centuries, and nothing but the reaching of a superior snow- 
line, where the dryness of the upper air forbids the formation 
of snow, would prevent the transference of our oceans from 
their beds to mountain summits. “ Supposing, at a particular 
point above the line referred to, a layer of three feet a year 
is added to the mass ; this deposit, accumulating even 
through the brief period of the Christian era, would produce 
an elevation of 5,580 feet. And did such accumulations 
continue throughout geologic instead of historic ages, we 
cannot estimate the height to which the snows would pile 
themselves."* But our mountains do not thus perceptibly 
grow higher ; what is it takes their increasing burden away, 
and enables the rhythm of nature to flow on here as elsewhere ? 
It is the glacier which removes the annual load of snow from 
the mountain sides, and, by its liquefaction, finally restores to 
the ocean water which may have been lifted from it some 
centuries before. Concerning this an eminent man of science 
has recently said, “ Is it not very remarkable that ice, by 
special properties which belong exclusively to it, has a move- 
ment which probably is the only one slow enough to remove 
in a continuous manner, without entirely ceasing, the sur- 
charged reservoirs of snow heaped upon the summits and 
plateaux of high mountains ? At the same time the ice itself 
descends into cultivated valleys, without producing there 
periodic cataclysms, but, on the contrary, originating those 
rivers that the heat of summer enlarges, and which carry 
freshness and fertility into the plain. How admirable a com- 
bination of the forces of nature, that a superior Intelligence 
could alone co-ordinate with a determinate end in view ! But 
even this is only a feeble scintillation of transformations, as 
grand as they are innumerable, continually taking place in the 
laboratory of nature, of which God alone is the master, but 
into the mysteries of which man is permitted to glimpse." 
But the snow on the mountain summits is a dry, white 
powder, whilst the glacier is composed of clear, solid ice. 
How can the one be transformed into the other ? 
Tyndall’s “ Heat,” 2nd edition, p. 18G. 
