nt beautiful glaciers. In the Tyrol, on the contrary, as
well as in Norway and Sweden, we find glaciers almost as fine as those
of Switzerland, in mountain-ranges much lower than either of the
above-named chains. But they are of diversified forms, and have valleys
widening upward on the slope of long crests. The glaciers on the
Caucasus are very small in proportion to the height of the range; but on
the northern side of the Himalaya there are large and beautiful ones,
while the southern slope is almost destitute of them. Spitzbergen and
Greenland are famous for their extensive glaciers, coming down to the
sea-shore, where huge masses of ice, many hundred feet in thickness,
break off and float away into the ocean as icebergs. At the Aletsch in
Switzerland, where a little lake lies in a deep cup between the
mountains, with the glacier coming down to its brink, we have these
Arctic phenomena on a small scale; a miniature iceberg may often be seen
to break off from the edge of the larger mass, and float out upon the
surface of the water. Icebergs were first traced back to their true
origin by the nature of the land-ice of which they are always composed,
and which is quite distinct in structure and consistency from the marine
ice produced by frozen sea-water, and called "ice-flow" by the Arctic
explorers, as well as from the pond or river ice, resulting from the
simple congelation of fresh water.

Water is changed to ice at a certain temperature under the same law of
crystallization by which any inorganic bodies in a fluid state may
assume a solid condition, taking the shape of perfectly regular
crystals, which combine at certain angles with mathematical precision.
The frost does not form a solid, continuous sheet of ice over an expanse
of water, but produces crystals, little ice-blades, as it were, which
shoot into each other at angles of thirty or sixty degrees, forming the
closest net-work. Of course, under the process of alternate freezing and
thawing, these crystals lose their regularity, and soon become merged in
each other. But even then a mass of ice is not continuous or compact
throughout, for it is rendered completely porous by air-bubbles, the
presence of which is easily explained. Ice being in a measure
transparent to heat, the water below any frozen surface is nearly as
susceptible to the elevation of the temperature without as if it were in
immediate contact with it. Such changes of temperature produce
air-bubb