Architecture of Snow.

We now resemble persons who have climbed a difficult peak, and thereby earned the enjoyment of a wide prospect.  Having made ourselves masters of the conditions necessary to the production of mountain snow, we are able to take a comprehensive and intelligent view of the phenomena of glaciers.

[Illustration:  SNOW CRYSTALS.]

A few words are still necessary as to the formation of snow.  The molecules and atoms of all substances, when allowed free play, build themselves into definite and, for the most part, beautiful forms called crystals.  Iron, copper, gold, silver, lead, sulphur, when melted and permitted to cool gradually, all show this crystallizing power.  The metal bismuth shows it in a particularly striking manner, and when properly fused and solidified, self-built crystals of great size and beauty are formed of this metal.

[Illustration:  SNOW-STAR.]

[Illustration:  SNOW-STAR.]

If you dissolve salt-petre in water, and allow the solution to evaporate slowly, you may obtain large crystals, for no portion of the salt is converted into vapor.  The water of our atmosphere is fresh though it is derived from the salt sea.  Sugar dissolved in water, and permitted to evaporate, yields crystals of sugar-candy.  Alum readily crystallizes in the same way.  Flints dissolved, as they sometimes are in nature, and permitted to crystallize, yield the prisms and pyramids of rock crystal.  Chalk dissolved and crystallized yields Iceland spar.  The diamond is crystallized carbon.  All our precious stones, the ruby, sapphire, beryl, topaz, emerald, are all examples of this crystallizing power.

[Illustration:  SNOW-STAR.]

You have heard of the force of gravitation, and you know that it consists of an attraction of every particle of matter for every other particle.  You know that planets and moons are held in their orbits by this attraction.  But gravitation is a very simple affair compared to the force, or rather forces, of crystallization.  For here the ultimate particles of matter, inconceivably small as they are, show themselves possessed of attractive and repellent poles, by the mutual action of which the shape and structure of the crystal are determined.  In the solid condition the attracting poles are rigidly locked together; but if sufficient heat be applied the bond of union is dissolved, and in the state of fusion the poles are pushed so far asunder as to be practically out of each other’s range.  The natural tendency of the molecules to build themselves together is thus neutralized.