Wherever King Frost waves his sceptre, one result always follows. Water changes from a liquid to a solid.
Nor is water the only liquid which so changes. Quicksilver, known to us usually as a liquid, may be frozen, though not without a greater amount of cold than that which freezes water. Then, again, molten iron—that is, iron made soft through great heat—is a liquid which when cold hardens into a solid. Iron as we most often see it is simply in its frozen state; just as much the frozen form of iron as ice is the frozen form of water.
And the freezing of the two comes about in the same mode. As molten iron cools and hardens it crystallizes. Minute needles, far too minute to be seen, take shape, crossing and re-crossing at various angles, till the whole becomes a solid mass of interlaced iron needles, held in position by attraction. When water changes into ice, the same thing happens. The water-particles shape themselves into tiny needles, and these ice-needles cross and re-cross, till they are knitted into a compact mass, something like the mass of iron needles.
Nor are needles alone found in ice. Exquisite forms resembling ice-flowers are there also, commonly invisible, but composed of ice-needles woven into various shapes, which again are woven into the fabric of the solid ice. So a block of ice may perhaps be said to be formed of ice-flowers, and the ice-flowers to be formed of ice-needles.
Such flowers are of many shapes, but more generally they have six petals each. If a ray of sunlight is thrown upon a slab of ice, through a lens, so as to concentrate the heat, then, as the ice melts, the sparkling of these tiny florets can be seen; and when their magnified image is cast upon a sheet, the six-petalled flowers become clearly visible.
Even more beautiful than the ice-flowers embedded in solid ice are the ice-flowers embedded in snow. They too are made of tiny spicules or needles of ice; and they too, while varying much in shape, are commonly six-petalled.
Solid blocks of ice are at first sight so unlike masses of feathery snow that a child would be surprised to hear a snowflake spoken of as “ice.” Yet the difference between the two lies mainly in the arrangement of the little ice-needles, in the way they are put together. Those of hard ice are more densely packed; those of snow are more loosely joined, with open spaces between, full of air. It is the abundance of air, mixed in with ice-needles, catching and reflecting light, which gives to snow its whiteness.
In some cases, however, as with glacier-ice, the texture is so close—like that of glass—that neither flowers nor needles are discernible.
The fact that snow may be, through hard pressure, actually transformed into firm ice—and this is an everyday occurrence in the high Alps—shows how closely akin the two are.
Every country in the world has, at a certain height, that which is called “the line of perpetual snow,” or, more briefly, “the snow-line.” Below that limit snow may fall in winter, and water may freeze, but both vanish in the summer. Above that limit snow and ice are found all the year round, lessening to some extent in summer months, but never disappearing.