pressed out, and the snow-crystals themselves are squeezed into
one solid mass of pure, transparent ice.

Then we have what is called a "glacier," or river of ice, and
this solid river comes creeping down till, in Greenland, it
reaches the edge of the sea. There it is pushed over the brink of
the land, and large pieces snap off, and we have "icebergs."
These icebergs - made, remember, of the same water which was
first draw up from the tropics - float on the wide sea, and
melting in its warm currents, topple over and over* (A floating
iceberg must have about eight times as much ice under the water
as it has above, and therefore, when the lower part melts in a
warm current, the iceberg loses its balance and tilts over, so as
to rearrange itself round the centre of gravity.) till they
disappear and mix with the water, to be carried back again to the
warm ocean from which they first started. In Switzerland the
glaciers cannot reach the sea, but they move down into the
valleys till they come to a warmer region, and there the end of
the glacier melts, and flows away in a stream. The Rhone and many
other rivers are fed by the glaciers of the Alps; and as these
rivers flow into the sea, our drop of water again finds its way
back to its home.

But when it joins itself in this way to its companions, from whom
it was parted for a time, does it come back clear and transparent
as it left them? From the iceberg it does indeed return pure and
clear; for the fairy Crystallization will have no impurities, not
even salt, in her ice-crystals, and so as they melt they give back
nothing but pure water to the sea. Yet even icebergs bring down
earth and stones frozen into the bottom of the ice, and so they