SPRING WATER. 241 
the surface of the water, and thus preserves from the 
effects of the surrounding cold, a vast body of heat in 
the fluid beneath ; and is itself ready to receive its own 
accustomed quantity upon the first change of the atmo- 
sphere. The expansion of water, in freezing, is owing 
to its assuming a crystallized form ; and this expansion 
is often so great that glass bottles, filled with water, are 
burst by it. 
During the intense cold of winter, snow, which is of a 
soft and spongy texture, is considered of great utility in 
preventing the immediate access of the atmospheric air 
to the ground ; it has doubtless been designed by Pro- 
vidence as a garment to protect the incipient vegetation, 
at that inclement season, from injury. 
The inhabitants of all the extreme northern parts of 
the world use thawed snow for their constant beverage 
during winter; and the vast masses of ice which float in 
the polar seas afford an abundant supply of fresh water 
to the navigators of those dreary regions. Snow water 
has, however, long lain under the imputation of occasion- 
ing those extraordinary swellings in the neck, which 
deform the inhabitants of some of the alpine valleys of 
Switzerland; but this opinion is not supported by any 
well-authenticated facts. Indeed it is rendered quite 
improbable by the frequency of this disease in the island 
of Sumatra, where ice and snow are never seen : and by 
its being quite unknown in Chili and Thibet, though 
the rivers of these countries are chiefly supplied by the 
melting of the snows. 
276. SPRING WdTER is nothing more than rain water, 
which having gradually filtered through the earth, collects at 
the bottom of declivities, and there makes its way to the surface. 
It is obvious that spring water must be nearly as various in 
its contents as the substances through which itjlows. 
Ordinary springs pass insensibly into mineral springs, 
according as their foreign contents become more abun- 
dant; but it 1ms not unfreqtiently happened that waters 
have acquired great medical reputation from their 
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