h
poles of this description, which compel the particles to lay
themselves together in a definite order, and you have before your
mind's eye the unseen architecture which finally produces the visible
and beautiful crystals of the snow. Thus our first notions and
conceptions of poles are obtained from the sight of our eyes in
looking at the effects of magnetism; and we then transfer these
notions and conceptions to particles which no eye has ever seen. The
power by which we thus picture to ourselves effects beyond the range
of the senses is what philosophers call the Imagination, and in the
effort of the mind to seize upon the unseen architecture of crystals,
we have an example of the "scientific use" of this faculty. Without
imagination we might have _critical_ power, but not _creative_ power
in science.

Architecture of Lake Ice.

We have thus made ourselves acquainted with the beautiful snow-flowers
self-constructed by the molecules of water in calm, cold air. Do the
molecules show this architectural power when ordinary water is frozen?
What, for example, is the structure of the ice over which we skate in
winter? Quite as wonderful as the flowers of the snow. The observation
is rare, if not new, but I have seen in water slowly freezing
six-rayed ice-stars formed, and floating free on the surface. A
six-rayed star, moreover, is typical of the construction of all our
lake ice. It is built up of such forms wonderfully interlaced.

Take a slab of lake ice and place it in the path of a concentrated
sunbeam. Watch the track of the beam through the ice. Part of the beam
is stopped, part of it goes through; the former produces internal
liquefaction, the latter has no effect whatever upon the ice. But the
liquefaction is not uniformly diffused. From separate spots of the ice
little shining points are seen to sparkle forth. Every one of those
points is surrounded by a beautiful liquid flower with six petals.

Ice and water are so optically alike that unless the light fall
properly upon these flowers you cannot see them. But what is the
central spot? A vacuum. Ice swims on water because, bulk for bulk, it
is lighter than water; so that when ice is melted it shrinks in size.
Can the liquid flowers then occupy the whole space of the ice melted?
Plainly no. A little empty space is formed with the flowers, and this
space, or rather its surface, shines in the sun with the lustre of
burnished silver.

In all cases the flowers