Imagine the molecules of water in calm cold air to be gifted with 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 are formed parallel to the surface of freezing.  They are formed when the sun shines upon the ice of every lake; sometimes in myriads, and so small as to require a magnifying glass to see them.  They are always attainable, but their beauty is often marred by internal defects of the ice.  Every one portion of the same piece of ice may show them exquisitely, while a second portion shows them imperfectly.