Snow crystal

“ They do not always take the same form, but follow the same laws that govern the formation of ice crystals. The structure of a snowflake may be often found upon a window pane of a frosty morning. Here, however, the free arrangement of the parts of a snow crystal are interfered with by its contact with the window pane, but while floating gently in the air there is the utmost freedom for the play of nature's forces as they apply to the work of crystallization. ”

“ The weather all day has been more or less overcast with white broken alto-stratus, and for 3 degrees above the horizon there is a grey belt looking like a blizzard of drift, but this in reality is caused by a constant fall of minute snow crystals, very minute. Sometimes instead of crystal plates the fall is of minute agglomerate spicules like tiny sea-urchins. The plates glitter in the sun as though of some size, but you can only just see them as pin-points on your burberry. So the spicule collections are only just visible. Our hands are never warm enough in camp to do any neat work now. ”

“ Just as alum crystallizes and rock crystal assumes varied and beautiful forms, so ice crystallizes into six-rayed stars.
It is to Professor Tyndall that the world is chiefly indebted for the descriptions of snow crystals and ice flowers. In his work upon “Heat as a Mode of Motion,” this charming writer shows us the structure of ice flowers. He describes a snow shower as a “shower of frozen flowers.” “When snow [Pg 640] is produced in calm air,” he says, “the icy particles build themselves into stellar shapes, each star possessing six rays.” ”

“ Although certain types of snow crystals may be detected with the naked eye, most of them are so tiny that their structural form cannot be determined without the aid of a microscope. If you chance to be out of doors during a snowfall, and happen to wear a dark coat of wool material, observe closely the flakes which chance to alight upon your sleeve and perhaps you may be able to recognise a true crystal. ”

“ They give no shelter or support to any created thing. They suffice for themselves, and stand out clearly defined in their distinct and independent existence. The surface of the snow is barren; the chilly glacier has no communion with the mountain glen through which it passes. The clear, sharp-cut crystal harbors no stain from earth or sky to show its sympathy with the materials out of which it sprang. The marble rock, like the snow, does not invite the green things of the soil around it to share its existence with it, and give to and take from it an element of picturesqueness and beauty. ”

“ Indeed the exquisite tracery of these snow crystals appears to afford a visual proof of the existence of the trigonal-hexagonal space-lattice as the framework of the crystal structure of ice. When one considers the countless numbers of such beautiful gems of nature’s handiwork massed together on an extensive snow-field of the higher Alps—such as that of the Piz Palü in the Upper Engadine, shown in Fig. ”

“ There have not been so many beautiful snow crystals in any storm of the winter. You may see half a dozen different varieties on your coat sleeve with the naked eye, and you pull out a strong lens the better to observe the exceeding beauty of these six pointed stars. They are among Nature's most exquisite [Pg 34] forms, and they are shown in bewildering variety. The molecules of snow arrange themselves in crystals of the hexagonal system, every angle exactly sixty degrees. The white color of the snow is caused by a combination of the prismatic colors of these snow crystals. ”

“ Nature, it seems, is ever versatile and the rarity of her patterns is practically inexhaustible.
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Unlike the mineral crystals, or those found in the mineral kingdom, which form beneath the surface of the earth, and are dependent largely upon their surroundings and environments for their crystalline formation, the snow crystal is most ethereal ”

“ Columnar six-sided type. Singular effect of miniature photographs enclosed
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Water itself as a liquid is to all appearances formless; when sufficiently cooled, however, the molecules are brought within play of the crystallising force, and thus arrange themselves in more or less attractive crystals. A most interesting point, well worthy of consideration, is that it is extremely improbable that anyone has as yet found, perhaps never will find, the one preëminently beautiful and symmetrical snow crystal which nature has probably fashioned in her most artistic mood—her masterpiece. ”

“ Snow crystals often continue to grow so long as they are in the atmosphere; but if they pass through an under-saturated stratum of air or a stratum whose temperature is above 32° Fahr., they suffer from evaporation or melting. When they reach the ground, the processes of growth and decadence continue, and the crystals grow or diminish according to circumstances.
A glacier is a colossal aggregation of crystals grown from snowflakes to granules of much greater sizes. The microscopic study of new-fallen snow reveals the mode of change from flakes to granules. ”

“ It is like a crowd of people passing from a broad thoroughfare into a narrow street. As the valley grows narrower and narrower the great mass of snow in front cannot move down quickly, while more and more is piled up by the snowfall behind, and the crowd and crush grow denser and denser. In this way the snow is pressed together till the air that was hidden in its crystals, and which gave it its beautiful whiteness, is all pressed out, and the snow-crystals themselves are squeezed into one solid mass of pure, transparent ice. ”

“ As they grow, the crystal prisms extend downwards. This gives a columnar or prismatic structure to the ice, well seen when it is “honeycombed” by partial melting. In the glacier, on the other hand, the crystals, starting from snowflakes, have their axes turned in various directions according to the accidents of their fall; and as the snow develops into ice, the principal axes of the 313crystals continue to lie in all directions. Hence glacier ice, unlike pond ice, cannot usually be split along definite planes, except where cleavage planes are subsequently developed by extraneous agencies. ”

“ Snow is composed of small colourless crystals of ice, the flat surfaces of which reflect, undecomposed, the light falling on them. The smaller are the crystals, the more pure appears to us the whiteness of the snow, and the thinner is the layer of snow required to produce the sensation of whiteness. But if the snow crystals are larger, the white appears to have a bluish tinge, and only a thick layer of snow is opaque. White lead, being an amorphous substance in a condition of very fine division, reflects the light very regularly, so that a thin layer of white lead appears quite opaque. ”

“ It is asserted by some observers that many of the lines or rods seen in the interior of snow crystals are really tubes filled with air.
Perfect crystals are by no means always common in snow storms, most of the forms produced being more or less unsymmetrical or otherwise imperfect. It rarely happens that during a single winter there are more than a dozen good opportunities for securing
complete crystals, and there may not be half so many. ”

“ Snow is ice in the form of light flocculent crystals, is it not? Why, at home, if you take up moist snow and press it hard in your hands, you can almost turn it into ice. If you placed it in a press, and applied much force, it would become perfectly clear ice. Well, there’s pressure enough here to turn it into ice ”

“ The snow storm to our limited understanding, begins with a miracle—the miracle of crystallization. Why should water freezing freely in the air be a part of geometry, the six rays of the snow [95] crystal growing at an angle one to another, of sixty degrees? ”

“ While rain is often the final product of snow that melts before it reaches the ground, snow is probably never formed from raindrops, but always condensed115 directly from water vapor. The finest snow consists of separate ice crystals, while snowflakes of larger sizes are always made up of several crystals partly melted together. The flakes on rare occasions attain a diameter of three or four inches, and larger sizes have been reported.
For ages mankind has admired the diversity of beautiful forms exhibited by snow crystals. ”

“ In these high regions, the heavy precipitation is always in the form of snow which keeps the great rock-basins full to over-flowing. The prodigious weight of the mass compacts the under-snows into clear crystal ice. To illustrate: if you take a handful of snow, squeeze it until it becomes a transparent crystal and then let it freeze, you have the counterpart of glacier-ice. ”

“ This is one of the most imperfect forms of snow crystallization, and occurs generally at a temperature but little above freezing, and at the commencement of a severe and continued frost, or immediately preceding a general thaw.
At other times a light feathery snow may be seen to fall, composed almost entirely of stars of six spiculæ or radii, united in the centre by a white molecule. These are seldom less than from four to five tenths of an inch in diameter, and are generally collected in tufts of half-a-dozen or more together, which in calm{136} weather waft uninjured to the ground. ”

“ There are many more difficulties to be encountered by crystal photographers in the study of ice formation, and its minute detail, than in that of either the snow or frost. Still many instructive and very interesting experiments have been made and facts obtained relating to the formation of the ice, and it has recently been possible to secure a valuable set of photographs which are wonderfully interesting, inasmuch as they serve to show the singular formation and development of ice crystal structure from start to finish. ”

“ In crystallography the photomicrograph is useful. Figs. 13-18 illustrate the appearance in polarized light of a few crystals of both organic and inorganic substances. Perhaps one of the richest of all substances in variety of form of crystals is snow. While the geometrical form is invariably hexagonal, it occurs in countless combinations and many of the crystals are very beautiful. For procuring pictures of snow crystals it seems necessary to use the apparatus in a temperature below the freezing point. ”

“ The crystal rock under microscopic examination shows the same beautiful figures and marvelous lines of arrangement that in winter the new fallen snow-flakes exhibit, and indicate that the lines of form are essentially the same that gave the planetary rock its forms of crystalline beauty and massive structure. And the beautiful snow that falls so gently upon the wintry lap of earth is one of the best representatives of creative power acting in the primitive states of formative forces. ”

“ The night had come on, but the air was bright, and in the limpid crystal of the lake, where the lines of the horizon were indistinguishable in the twilight, I seemed to trace and follow the immensity of the starry heavens, and to float, like a disembodied spirit, upon some fantastic similitude of infinity. Ah, Monsieur Goefle! how strange is life sometimes! ”

“ Greely’s observations at Fort Conger show that, varied as are the forms of snow crystals, those that fall during any particular storm are invariably of the same types, even though they may be collected from localities widely removed from each other. All crystals of snow are hexagonal in plan, but there is much variety in detail. The laws that produce one variety at one time, and a second at another, are not yet known. ”

“ Snow-flakes that come from the cold regions of the air, three or four miles high, generally have a solid form. All, of course, show the six-sided form of the snow crystals. Being smaller and heavier in proportion to their surface they fall more quickly. In the layers of the atmosphere, one or two miles high, where the air is not as cold and where the content of water vapor is higher, the flakes have more opportunity to grow as they slowly sink through the air. ”

“ The above are some of the more important of the many interesting results which have come from our study of snow crystals. They are given not merely as of value in themselves, but also in the hope that others may be stimulated to undertake similar investigations, and that thus our knowledge of these charming objects may be greatly increased. ”

“ 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.
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 [pg 349] and, for the most part, beautiful forms called crystals. ”

“ No less than a thousand different forms of delicate crystals have been found among snowflakes, but though there is such a great variety, yet they are all built on the six-sided and six-pointed plan, and are all rendered dazzlingly white by the reflection of the light from the faces of the crystals and the tiny air-bubbles built up within them. This, you see, is why, when the snow melts, you have only a little dirty water in your hand; the crystals are gone and there are no more air-bubbles held prisoners to act as looking-glasses to the light. ”