ICE, a solid, transparent, and brittle body, formed of some fluid, particularly water, by means of cold.
M. Lemery observes, that ice is only a re-establishment of the parts of water in their natural state; that the mere absence of fire is sufficient to account for this re-establishment; and that the fluidity of water is a real fusion, like that of metals exposed to the fire; differing only in this, that a greater quantity of fire is necessary to the one than the other. Galileo was the first who observed that ice was lighter than the water which composed it; and hence it happens that ice floats upon water, its specific gravity being to that of water as eight to nine. This rarefaction of ice seems to be owing to the air-bubbles produced in water by freezing, and which, being considerably large in proportion to the water frozen, render the body so much specifically lighter. These air-bubbles, during their production, acquire a great expansive power, so as to burst the containing vessels, though ever so strong.
M. Mairan, in a dissertation on ice, attributes the increase of its bulk chiefly to a different arrangement of the parts of the water from which it is formed; the icy skin on the water being composed of filaments, which, according to him, are found to be constantly and regularly joined at an angle of 60°; and which, by this angular disposition, occupy a greater volume than if they were parallel. He found the augmentation of the volume of water by freezing, in different trials, a fourteenth, an eighteenth, a nineteenth, and, when the water was previously purged of air, only a twenty-second part; that ice, even after its formation, continues to expand by cold; for, after water had been frozen to some thickness, the fluid part being let out by a hole in the bottom of the vessel, a continuance of the cold made the ice convex; and a piece of ice which was at first only a fourteenth part specifically lighter than water, on being exposed some days to the frost, be-
came a twelfth part lighter. To this cause he attributes the bursting of ice on ponds.
Though it has been generally supposed that the natural crystals of ice are stars of six rays, forming angles of 60° with each other, yet this crystallization of water, as it may properly be called, seems to be as much affected by circumstances as that of salts. Hence we find a considerable difference in the accounts of those who have undertaken to describe these crystals. M. Mairan informs us that they are stars with six radii; and his opinion is confirmed by observing the figure of frost on glass. M. Romé de l'Isle determines the form of the solid crystal to be an equilateral octahedron; M. Hassenfratz found it to be a prismatic hexahedron; but M. d'Antic found a method of reconciling these seemingly opposite opinions. In a violent hail-storm, where the hailstones were very large, he found that they had sharp wedge-like angles of more than half an inch; and in these he supposed it impossible to see two pyramidal tetrahedra joined laterally, and not to conclude that each grain was composed of octahedrons converging to a centre. Some had a cavity in the middle; and he saw the opposite extremities of two opposite pyramids, which constitute the octahedron; he likewise saw the octahedron entire united in the middle; all of them were therefore similar to the crystals formed upon a thread immersed in a saline solution. On these principles M. d'Antic constructed an artificial octahedron resembling one of the largest hailstones, and found that the angle at the summit of the pyramid was 45°, but that of the junction of the two pyramids 145°. It is not, however, easy to procure regular crystals in hailstones, where the operation is conducted with such rapidity; in snow and hoar-frost, where the crystallization goes on more slowly, our author is of opinion that the rudiments of octahedra may be discovered. (See the section on CONGELATION, in the article COLD.)
Blink of the Ice, is a name given by the pilots to a bright appearance near the horizon, occasioned by the ice, and observed before the ice itself is seen.
Ice-Boats, boats so constructed as to sail upon ice, and which are very common in Holland. They go with incredible swiftness, sometimes so quickly as to affect the breath, and are found very useful in conveying goods and passengers over lakes and great rivers. Boats of different sizes are placed in a transverse form upon a two-and-a-half or three-inch deal board. At the extremity of each end are fixed irons, which turn up in the form of skaits. Upon this plank the boat rests, and the two ends serve as out-riggers to prevent oversetting; whence ropes are fastened that lead to the head of the mast in the nature of shrouds, and others passed through a block across the bowsprit. The rudder is made somewhat like a hatchet with the head placed downwards, which being pressed down, cuts the ice, and serves all the purposes of a rudder in the water, by enabling the helmsman to steer.
Ice-House, a repository for ice during the summer months. The aspect of ice-houses should be towards the east or south-east, for the advantage of the morning sun to expel the damp air, as that is more pernicious than warmth; for which reason trees in the vicinity of an ice-house tend to its disadvantage. The best soil for an ice-house to be made in is chalk, as it conveys away the waste water without any artificial drain; the next to that is loose stony earth or gravelly soil.
Ice may be preserved in a dry place under ground, by covering it well with chaff, straw, or reeds. Great use is made of chaff in some places of Italy to preserve ice; the ice-house for this purpose need only be a deep hole dug in the ground on the side of a hill, from the bottom of which they can easily carry out a drain, to let out the water which is separated at any time from the ice, that it
may not melt and spoil the rest. If the ground is tolerably dry, they do not line the sides with any thing, but leave them naked, and only make a covering of thatch over the top of the hole. This pit they fill either with pure snow, or else with ice taken from the purest and clearest water; because they do not use it, as we do in England, to set the bottles in, but really mix it with the wine. They first cover the bottom of the hole with chaff, and then lay in the ice, not letting it anywhere touch the sides, but ramming in a large bed of chaff all the way between; they thus carry on the filling to the top, and then cover the surface with chaff. Ice packed in this manner will keep as long as they please. When they take any of it out for use, they wrap up the lump in chaff, and it may then be carried to any distant place without waste or melting.
It appears from the investigations of Professor Beckman, in his History of Inventions, that the ancients, from the earliest ages, were acquainted with the method of preserving snow for the purpose of cooling liquors in summer. "This practice," he observes, "is mentioned by Solomon; and proofs of it are so numerous in the works of the Greeks and the Romans, that it is unnecessary for me to quote them, especially as they have been collected by others. How the repositories for keeping it were constructed we are not expressly told; but it is probable that the snow was preserved in pits or trenches.
"When Alexander the Great besieged the city of Petra, he caused thirty trenches to be dug, and filled with snow, which was covered with oak branches, and which kept in that manner for a long time. Plutarch says that a covering of chaff and coarse cloth is sufficient; and at present a like method is pursued in Portugal. Where the snow has been collected in a deep gulf, some grass or green sods, covered with dung from the sheep pens, is thrown over it; and under these it is so well preserved, that, the whole summer through, it is sent the distance of sixty Spanish (nearly 180 English) miles to Lisbon.
"When the ancients, therefore, wished to have cooling liquors, they either drank the melted snow, or put some of it in their wine; or they placed jars filled with wine in the snow, and suffered it to cool there as long as they thought proper. That ice was also preserved for the like purpose, is probable from the testimony of various authors; but it appears not to have been used so much in warm countries as in the northern. Even at present snow is employed in Italy, Spain, and Portugal; but in Persia ice. I have never any where found an account of Grecian or Roman ice-houses. By the writers on agriculture they are not mentioned."
Ice-Island, a name given by sailors to a great quantity of ice collected into one huge solid mass, and floating about upon the seas near or within the polar circles. The motion of the lesser pieces is as rapid as the currents: the greater, which are sometimes two hundred leagues long, and sixty or eighty broad, move slowly and majestically; often fix for a time, immovable by the power of the ocean, and then produce near the horizon that bright white appearance called the ice-blink. The approximation of two great fields produces a most singular phenomenon; it forces the lesser (if the term can be applied to pieces of several acres square) out of the water, and adds it to the surface; a second, and often a third succeeds, so that the whole forms an aggregate of a tremendous height. These float in the sea like so many rugged mountains, and are sometimes five or six hundred yards thick; but the far greater part is concealed beneath the water. These are continually increased in height by the freezing of the spray of the sea, or the melting of the snow which falls on them. Those which remain in this frozen climate receive continual additions; others are gradually wafted by the northern
Icebergs winds into southern latitudes, and melt by degrees by the heat of the sun, till they waste away, or disappear in the boundless element.