Ice 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. ”

“ Plate X. Photograph of a cast made by pouring plaster over a surface of mud in which ice crystals had recently formed, in Rock Island, Ill., and where they had later been removed by natural sublimations into the atmosphere, leaving open cracks in the mud. It will be seen that the crystal growth in this case involves an x-like or radiating pattern formed of relatively very slender forms that almost everywhere are very gently curved somewhat reminding of the slender thread-like crystals sometimes seen in frost on windows. ”

“ Every wave, by contrast, and by some optical effect, nearly black as it approaches, is instantly changed into the loveliest green as it rolls up to the silvery bright ice. And all the adjacent deep is a luminous pea-green. The eye follows the ice into its awful depths, and is at once startled and delighted to find that the mighty crystal hangs suspended in a vast transparency, or floats in an abyss of liquid emerald. ”

“ 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. ”

“ Plate III. Photograph of fossil casts of a close tangle of ice crystals seen in a stony calcareous layer in the Eagle Ford shale in Walnut Creek, about eight miles north of Austin, Texas. This tangle is closer than any of the recent ice crystal marks figured here, but equally closely grown crystals have been seen by the writer on frozen mud in Illinois. Natural size. ”

“ 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.” ”

“ Here again we need none of Vulcan's aid, for we all know that when once crystallization commences each little crystal will have its growth in spite of almost any resistance. Witness the growth of ice crystals in our water pipes in zero weather. In other words, the force exerted by growing crystals is known to be at least of the same order of magnitude as the crushing strength of the grown crystal. ”

“ The spot is a vacuum. Such is the faithfulness to herself with which Nature operates; thus, in all her operations, does she submit to her own laws. We know that ice, in melting, contracts; and here we arrest the contraction, as it were, in the very act. The water of the flowers cannot fill the space occupied by the ice which by its fusion has given birth to them; hence the production of a vacuum, the inseparable companion of each liquid flower.
The fragment of compact ice whose elements assume such beautiful crystalline forms is itself a crystal. ”

“ Each little fragment of ice has a separate glitter of its own, so that the whole surface sparkles with a frosted radiance. It is not the same at dawn after a cold night, for then there is no water between the fragments, but all is hard and solid. No sooner, however, does the sun shine upon them, than the bonds are released and the ice-crystals begin to break up with a gentle tinkling sound and little flashes of light reflected from tiny wet mirror-surfaces. One can spend hours watching these small phenomena as happily as gazing upon the great mountains themselves. Size is a relative term. ”

“ Now and again the swell, in which fragments of ice floated with the gleam of crystal in liquid glass, would be too quick for our dull rise and overflow the bed, brimming to the channels with much noise of foam and pouring waters, but the interposition of the ice took half its weight out of it, and it never did more than send a tremble through the vessel. ”

“ Frequently they remain in this stage of development for some time without further change, but when it is zero weather they quickly increase in growth, and soon begin to show clearly defined scallops as shown in photograph No. 130.
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In No. 131, the ice crystal has at last begun to assume definite form, and its hexagonal shape is more clearly defined; while in No. 132, we have the completed flower-like outline, and in Nos. 133 and 134 the finished ice flower with its air inclusions of light and shade perfected. ”

“ In cases of this kind one always looks for corroborating facts to check one's conclusions. I found this check in the discovery of the layer which carries ice crystal markings [p.8] in these beds. The layer had a definite relation to the seams of bentonite, and, with this additional evidence, I was confident there was no possible chance of a mistake. It enabled me to locate not only the right horizon but also a horizon in the underlying heavy Comanchean limestone, which is water-bearing, and which must be avoided to prevent serious injury to the underground operations. ”

“ 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. ”

“ When the ice flowers or crystals first begin to appear, it is usually upon the surface of the water, and close to the sides of the pail. Frequently they push out in long, delicate, needle- or lance-like forms while upon the plain edges of these sharp lances, scallops and delicate serrations quickly follow. But the individual or flower type of crystals which grow and scatter themselves over the surface of the water, do not attach themselves to any object, but grow in a detached fashion, and are really the most interesting crystal for observation and study. ”

“ That evaporation which is steadily going on from the surface of ice even in the coldest weather, the crystals passing to vapor without the intervening stage of water, had worn off the embossing. The ice instead of being black was gray with countless air bubbles all through its texture. You will always find these after a day’s clear sun on a first freezing. I fancy the ice crystals make minute burning glasses under the sun’s rays and thus cause tiny meltings within its own bulk, the steam of the fusing making the bubbles ”

“ The Pebble Crystals of England are often of very considerable Hardness; and some have been found here which the Lapidaries have said approached to the white Sapphire. The pointed and hexangular are what Authors have called Iris's and Pseudo-adamantes. The Antients were of opinion, that Crystal was only Water congealed in long tract of Time, into an Ice, more durable than the common. And Pliny thought it was no where to be found but in excessively cold Regions; but we are now very certain, that it is even in the hottest. ”

“ I reminded him of his having spoken of crystals of ice, and asked how that term could be applied to any thing but mineral bodies.
“The term crystal,” he replied, “came from the Greek word for ice—it was afterwards applied to rock crystal, which the ancients imagined to be water converted into stone; but it now signifies the regular figure in which the particles of any substance arrange themselves in passing from the liquid to the solid state.—Each of those sub{86}stances has a figure for its crystal peculiar to itself, and from which it never varies. ”

“ Ice soon begins to form on the inside and bottom of the cans under the influence of this intense cold. It becomes thicker and thicker, until it is finally a solid mass of clear crystal ice, usually with a small core of opaque or snowy ice, exactly through the centre. ”

“ If you observe very closely, you will discover that meanwhile, in the little open spaces, between the bolder fern-like designs, more delicate feathery forms are gradually appearing, formations which sometimes resemble fine coral branches. As soon as the water-film ice crystallisations are completed they are closely followed by the true frost crystals, which form upon the various dry places upon the glass, delicate lines and stars and also in a thin, dew-like deposit, which rapidly freezes, and assumes a granular, snow-like form. ”

“ When the heat rays from the lantern pass through such a slab of ice, the surface of which is focussed on the screen by a projecting lens, they cause the ice to begin to melt in numerous spots in the interior of the slab simultaneously; and the structure of the crystal is revealed by the operation occurring with production of cavities taking the shape of hexagonal stars, which when focussed appear on the screen as shown in Fig. ”

“ The markings figured by Professor Clarke are undoubtedly of the same kind as those I have found in the Eagle Ford. They occur in the Upper Devonian in New York. I also find that the formation of ice crystals in wet mud has been observed in the clays about Boston by Marbut and Woodworth. [B] Other observations of similar recent markings are said to have been made by some English geologists.
To "practical people" it may indeed appear that no more unprofitable or more idle curiosity could be indulged in, than making observations on what kind of crystals are formed when water freezes in mud. ”

“ 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. ”

“ Ice of this kind, resulting from the direct congelation of water, is easily recognized under all circumstances by its regular stratification, the alternate beds varying in thickness according to the intensity of the cold, and its continuance below the freezing-point during a longer or shorter period. Singly, these layers consist of irregular crystals confusedly blended together, as in large masses of crystalline rocks in which a crystalline structure prevails, though regular crystals occur but rarely. ”

“ If we hadn't our bewitching autumn foliage, we should still have to credit the weather with one feature which compensates for all its bullying vagaries—the ice-storm: when a leafless tree is clothed with ice from the bottom to the top—ice that is as bright and clear as crystal; when every bough and twig is strung with ice-beads, frozen dewdrops, and the whole tree sparkles cold and white, like the Shah of Persia's diamond plume. ”

“ The first appearance of ice, when in a state of detached crystals, is called by the sailors sludge, and resembles snow when cast into water that is too cold to dissolve it. This smooths the ruffled surface of the sea, and produces an effect like [Pg 69] oil in preventing breakers. These crystals soon unite, and would form a continuous sheet, but, by the motion of the waves, they are broken in very small pieces, scarcely three inches in diameter. As they strengthen, many of them coalesce, and form a larger mass. ”

“ The panes becoming colder and colder, these minute drops at last freeze, and the water not only becomes solid, but it crystallises; that is to say, the little solid masses take on more or less regular geometrical forms with flat faces, inclined to one another at constant angles, so that they resemble bits of glass cut according to particular fixed patterns. All ice is in fact crystalline, but in ice which has been formed from thick sheets of water, the crystals are so packed together that they cannot be distinguished separately. ”

“ It is not difficult to understand why ice should take more room; for we know that if we were to try to arrange bricks end to end in star-like shapes, we must leave some spaces between, and could not pack them so closely as if they lay side by side. And so, when this giant force of crystallization constrains the atoms of frozen water to grow into star-like forms, the solid mass must fill more room than the liquid water, and when the star melts, this space reveals itself to us in the bright spot of the centre. ”

“ UNSTRATIFIED ROCK.—A VOLCANIC BLOCK.
"Crystallization" means those particular forms or shapes in which the particles of a liquid arrange themselves, as that liquid hardens into a solid—in other words, as it freezes. Granite, iron, marble, are frozen substances, just as truly as ice is a frozen substance; for with greater heat they would all become liquid like water. When a liquid freezes, there are always crystals formed, though these are not always visible without the help of a microscope. ”