Ice lead

“ Balanced around its heart, far down in the deep, and in its cold solidity “dry as summer dust”—poised upon its centre with perfect exactness, it is evident that the loss of a single ton of ice shifts that centre, shifts it an ounce-notch on the bar of the mighty scale, destroys the equilibrium, and subjects the whole to the necessity of some small movement in order to regain its rest. ”

“ The weather now determines the lot of the ice dealer. As the cold breezes whistle over the water, stirring it into ripples, and breaking its surface into waves, a wonderful change is rapidly transforming its liquid pearls into flinty diamonds. Gradually the heat in the water is radiated into the air. As fast as the surface water is cooled, it is condensed, and sinks to the bottom, its place being taken by the warmer and lighter water from beneath. ”

“ 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. ”

“ This mass of snow and ice does not remain stationary, as might be expected from its apparent solidity. Under the influence of its own weight and of alternations of heat and cold, it flows down the incline like a very thick liquid. During the winter the ice melts but little, and the movement is slow, but in the summer, under the influence of the warm days and cool nights, both the melting and the rate of flow of the ice are increased. ”

“ If the earth has a fluid centre, and only a comparatively thin crust, as some suppose, there must be such tides, produced by the gravitation of the moon and sun.
Ice presents some interesting results of this viscosity. At a certain height, varying with latitude, aspect, etc., we reach the “snow line” of mountain slopes, above which the snow of winter remains unmelted during summer, and, in most cases, goes on accumulating. It soon loses its flocculent, flaky character, and becomes coherent, clear blue ice by the pressure of its own weight. ”

“ Summer and winter the snow is precipitated upon these mountains, and from time to time the heat of the sun's rays softens the snow, when by its great weight it packs more closely together until it is, in many cases, formed into solid ice-cakes. If we take a quantity of snow or a quantity of granulated ice and put it under a sufficient pressure we can produce clear solid ice, and it is by this process that ice is formed out of the snow and hail that falls continually upon the tops of these glacial mountains. ”

“ The ice once formed in such cavities, only melts slowly; for one knows that ice in melting, absorbs 60° of heat; and where find this heat in an air always very cold and nearly still? During a great cold, the ice forms with great promptness, while it melts with much slowness, even when the temperature of the air is several degrees above zero; what must then not be this slowness when the temperature of the interior air only rises in summer one degree above freezing point. It would need several summers to melt this ice if it did not reform each winter. ”

“ But, under all these various circumstances, frost will transform the crystalline snow into more or less compact ice, the mass of which will be composed of an infinite number of aggregated snow-particles, very unequal in regularity of outline, and cemented by ice of another kind, derived from the freezing of the infiltrated moisture, the whole being interspersed with air. Let the temperature rise, and such a mass, rigid before, will resolve itself again into disconnected ice-particles, like grains more or less rounded. ”

“ If you take a piece of this solid substance, you find it to be cold, brittle, and transparent. Brought into a warm room it soon melts into water, and you may drive off the water as before into vapor. Ice is the general name given to water when it is in the solid state, such forms as snow and hail being only different appearances which ice puts on. Whenever water becomes colder than a certain temperature it passes into ice, or freezes, and this temperature is consequently known as the freezing-point. ”

“ The rate at which ice is formed decreases as the thickness of the floe increases, and it ceases to be formed as soon as the floe becomes a non-conductor of the temperature of [4] the air by the increase of its mass, or when the driving of the ice-tables one over the other, or the enormous and constantly accumulating covering of snow, places limits to the penetration of the cold. ”

“ 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 ”

“ Sometimes when those floating pieces or plates meet with any obstruction in the channel of the river, they accumulate in such quantities as to cover the surface of the water, and become frozen together in one large sheet, but this kind of ice may be always readily distinguished from that produced in the usual way by the action of the cold air on the surface, which is smooth, transparent, and of an uniform texture ”

“ These layers of ice become numerous and are parallel to each other, like the layers of ice formed from slosh. Such crusts of ice I have myself observed again and again upon the glacier. This stratified snowy ice is now the bottom on which the first autumnal snow-falls accumulate. These sheets of ice may be formed not only annually before the winter snows set in, but may recur at intervals whenever water accumulating upon an extensive snow-surface, either in consequence of melting or of rain, is frozen under a sharp frost before another deposit of snow takes place. ”

“ The approximation of several fields of ice of different magnitudes, produces a very singular phenomenon. The smaller of these masses are forced out of the water, and thrown on the larger ones, until at length an aggregate is formed of a tremendous hight. These accumulated bodies of ice float in the sea like so many rugged mountains, and are continually increased in hight by the freezing of the spray of the sea, and the melting and then freezing of the snow which falls on them. ”

“ The tumbling and turning of the water at rapid shoals materially assists the growth of ice at points below where the current grows gentle. Streams of this character, whose beds are free from accumulations of vegetable mold, or other sources which generate gases, produce clear and sparkling ice of greater thickness than is found on still ponds or lakes in the same vicinity, and exposed to the same temperature. ”

“ This last stage of. development may also be attained without rain, should the sun have sufficient power to melt some of the ice; the water from which will then trickle down to the under-side of the roll of ice, and there form icicles in a similar manner. As the sun gains in power, the wire increases in temperature, and melts away more of the ice from within; the icicles, borne down by their own weight, drop lower and lower, until the wire reaches the extreme points of the upper row, when of course the whole congealed mass soon drops off. ”

“ Snow, however, in the event of soft or warm weather, is an aid to the ice by protecting it from the direct heat of the sun, and the force of a rain is largely expended in melting the snow. The water and snow on the top of the ice freezes into snow ice as soon as the weather turns cold again. ”

“ The change of snow into ice is owing to alterations of temperature, to partial melting and subsequent freezing, constantly renewed,—and also to the sinking of the mass upon itself in consequence of its own weight, the lower portions being thus forced out by the pressure of the superincumbent ice. ”

“ A stillness like death reigns over all the surrounding forms of ice, and the frozen ocean stretches out beneath a vast shroud. A sunless leaden sky spreads over all, not a breath of air stirs, it is neither warm nor cold, slowly melts the snow, and this pale realm of ice forms a world of danger and difficulty, against which are matched the strength and sagacity of three-and-twenty men! ”

“ It is ice, a point of the berg pricking up into the illuminated surface and reflecting the light. You will understand that better, perhaps, by and by. But wait an instant. Now!—now!—Beauty strikes the billow with her magic rod, and, presto—change!—all is glittering green. A thousand feet of purple, cloud-like wave passes, in the twinkling of an eye, into the brightness of an emerald gem, and thus rolls up and smites the iceberg. And thus, like night perpetually bursting into the splendid noon, roll up the billows, and strike the minutes of the hour. ”

“ There are also innumerable small cells in glacier-ice holding air and water; such cells also occur in lake-ice; and here they are due to the melting of the ice in contact with the bubble of air. Experiments are needed on glacier-ice in reference to this point.
22. At a free surface within or without, ice melts with more ease than in the centre of a compact mass. The motion which we call heat is less controlled at a free surface, and it liberates the molecules from the solid condition sooner than when the atoms are surrounded on all sides by other atoms which impede the molecular motion. ”

“ 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. ”

“ 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. ”

“ This broken-up ice is known as "Pack ice." During the breaking up of the ice, the floes crush together and their edges are broken and curled and piled with the pressure. Farther away from the open sea, well in among the solid floes, this pressure is very heavy and one floe may run over and another under the other. The edges of an extended crack, that has formed in a weak place, curl over and over and a long ridge of broken-up ice is the result. ”

“ The upper layer of this first surface of ice being elevated above the surface of the sea, will receive all the fresh water which falls from the atmosphere in the form of snow, sleet, rain or dew, by the successive congelation of which, the largest fields of ice may at length be formed.
It is a matter of little consequence to a navigator, whence the ice which supplies him with fresh water is produced. ”

“ As the ice thickens, its growth is slower at the same, or even a lower, temperature than that which at first made ice very rapidly. The earth at the bottom and sides of the ice field radiate heat into the water. The heat rays of the sun pass through the ice, if it is clear, into the water below, with very16 little effect upon the ice itself. The ice, being a poor conductor of heat, is, under these conditions, an obstacle to its own growth. ”

“ The expanding, shearing, breaking force of forming ice, the constant cutting of emery-edged running water, and the undermining thaw of spring sent thundering downward with ten thousand varying echoes a half-million tons of snow, ice, and stones. ”

“ The temperature most suitable for the formation of ice in nature is the temperature which remains the most steadily around the freezing-point of water. Extremes of temperature are not favourable to the formation of snow, which is the form in which water generally passes into glacier ice. ”

“ If we suppose a nearly symmetrical lump of ice, floating with that stable equilibrium which belongs to its excessive submergence, the atmosphere, which has now a temperature as high as 64° in the sunshine, will gradually round off and crease the edges, and at the same time will melt the portions of the mass which are above water. ”

“ As the ice is taken from the house, the covering of sawdust should be kept in place over the ice as far as possible. If58 the space over the ice is sealed up, the air, being above the freezing point, becomes saturated with moisture, which settles upon the ice, softening and melting it. When the outside air is cooler than that over the ice or in the loft, the moist air is driven out, if the ventilators are open. ”

“ A sheet of ice, of this kind, floating upon water, dissolves in the same manner, melting wholly from the surface, if the process be sufficiently rapid, or falling to pieces, if the air-bubbles are gradually raised in their temperature sufficiently to render the whole mass cavernous and incoherent. If we now compare these facts with what is known of the structure of land-ice, we shall see that the mode of formation in the two cases differs essentially.
Land-ice, of which both the ice-fields of the Arctics and glaciers consist, is produced by the slow and gradual transformation of snow into ice ”