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86 LIGHI AND WATER
contain nothing but what it gains from the atmosphere, and
it is distilled without the chance of those impurities which
may exist in the vessels used in an artificial operation. We
cannot well examine the water precipitated from the atmo¬
sphere as rain without collecting it in vessels, and all artificial
contact gives more or less of contamination; but in snow,
melted by the sunbeams, that has fallen on glaciers, them¬
selves formed from frozen snow, water may be regarded as
in its state of greatest purity. Congelation expels both salts
and air from water, whether existing below, or formed in, the
atmosphere; and in the high and uninhabited regions of
slaciers, there can scarcely be any substances to contamin¬
ate. Removed from animal and vegetable life, they are even
above the mineral kingdom; and though there are instances
in which the rudest kind of vegetation (forms of the fungus
or mucor kind) is even found upon snows, yet this is a rare
occurrence; and red snow, which is occasioned by it, is an
extraordinary and not a common phenomenon towards the
pole, and on the highest mountains of the globe. Having
examined the water formed from melted snows on glaciers
in different parts of the Alps, and having always found it
of the same quality, I shall consider it as pure water, and
describe its characters. Its colour, when it has any depth,
or when a mass of it is seen through, is bright blue; and,
according to its greater or less depth of substance, it has
more or less of this colour: as its insipidity and its other
physical qualities are not at this moment objects of your
inquiry, I shall not dwell upon them. In general, in exam¬
ining lakes and masses of water in high mountains, their
colour is of the same bright azure. And Captain Parry states,
that the water on the Polar ice has the like beautiful tint.
When vegetables grow in lakes, the colour becomes nearer
sea green, and as the quantity of impregnation from their
decay increases—greener, yellowish-green, and at length,
when the vegetable extract is large in quantity—as in coun¬
tries where peat is found—yellow, and even brown. To