146 ICARUS ICE 7,000. It is situated in a sandy plain, and the heat is excessive ; nevertheless, lea exports im- mense quantities of wheat and other grains, exquisite olive oil, and superior wines and brandies, through its port, Pisco, 48 m. N. N.W., to which place a railway has been in operation since 1872. The cost of the line was $1,364,- 062 50. An extensive trade is also carried on in fish taken on the Pacific coast. There are several schools, which are well attended. In the adjacent district are found species of stones called dentritis, which when polished present curious views of trees, plants, edifices, &c. H'lKl s. See DJJDALUS. ICE, water or other fluid solidified by freez- ing. Various liquids become partially solid at low temperatures, but this is commonly owing to the water of which they are in part com- posed ; and none of them produce a clear uni- form solid like that of frozen water. At 32 F. under ordinary circumstances water begins to crystallize. Slender prisms, usually of six sides, and terminated by six-sided pyramids, form in it, and arrange themselves in lines crossing each other at angles of 60' and 120. The presence of salts in solution impedes this process, and when at last it takes place at a temperature below 32, the greater portion of the foreign matter is excluded from the ice, which consequently is nearer the composition of pure water. Advantage is taken of this in some operations designed to concentrate the strength of liquors, as of vinegar, the portion that first crystallizes by cold being removed, and leaving the residue less diluted. Pure water contained in a polished vessel and kept perfectly quiet may be reduced to several de- grees below the freezing point without freez- ing; but agitation or the introduction of for- eign bodies will cause congelation to take place suddenly, and as the ice is formed latent heat is liberated, and the temperature rises to 32. Saline solutions sometimes exhibit a similar reluctance to deposit their salts in crystalline form even when reduced by evaporation below their point of saturation ; and in these cases crystallization is often suddenly induced by the same methods that cause the water to con- geal. From about 39 water expands as its tem- perature is reduced, with the exertion of pro- digious force. A hollow globe of brass with a cavity only an inch in diameter, filled with wa- ter, has been burst by the freezing of this, ex- erting a force, as estimated, of 27,720 Ibs. The effect of this property is seen in the tenden- cy of ice to plough up the banks of ponds, to split off masses of rock from mountain cliffs, and to loosen and pulverize the soil through which it is diffused. The effect last named is not perceived till the thaws of spring, when the frost is said to come out of the ground. This force has been artificially applied to split- ting rocks and trunks of trees by allowing water to freeze in their fissures. This expan- sion, estimated by Boyle at one ninth the ori- ginal volume, gives to ice less density than that of water, so that it floats. Its specific gravity by this estimate should be 0'9 ; M. Brunner in his series of experiments found it to vary from 0-918 at C. to 0-92025 at 20 0. But for this exception, which is however not a singu- lar one, to the usual law of increase of density by reduction of temperature, ice as it forms would sink to the bottom, and there accumu- late beyond the reach of atmospheric heat; great collections of water would be chilled throughout, and their fitness for sustaining life in cold regions be entirely destroyed. But as the ice, a bad conductor of heat, covers the water, it serves as a protecting sheet to retain the warmth below, and preserve the water from the extreme temperature that prevails above. As the cold increases, the solid ice is found to be subject to the usual law, contract- ing as found by Brunner more than other solids ; and upon ponds in excessively cold weather it contracts, and in shrinking parts asunder in the weakest places with loud re- ports. A form of ice called anchor ice is often seen in cold weather attached to objects at the bottom of streams. Its character is explained by Prof. Dewey on the supposition that the whole body of water is cooled below the freez- ing point, but under conditions of quietness opposed to the formation of ice. The sub- stances at the bottom serve as points of con- gelation, like those introduced into saline solu- tions to cause crystallization to take place, and ice forms upon them. It is observed to gather in a clear cold night, when the surface of the water is not frozen, and its temperature is at the freezing point, that of the air being still lower. The layers of ice are sometimes 3 in. thick ; and as soon as they are detached from the bodies which hold them down they rise to the surface. In some of the crevasses of the Alpine glaciers immense icicles from 20 to 30 ft. long were found by Tyndall, hanging from the coping of snow which lines the edges of the chasms. Near the poles, and on moun- tains at a certain height in all latitudes, there are immense masses of what may be considered permanent ice ; and there are said to be places in Siberia, even where there is a limited cul- ture of the ground, where ice is always found at a certain depth below the surface. In a well which was sunk at Yakutsk the earth was found firmly frozen to the depth of 382 ft., some of the strata being entirely of ice. From the exposed polar ice fields and glaciers great masses become detached and form icebergs. (See ICEBERGS.) The regelation of ice, a phe- nomenon first distinctly observed by Faraday, has recently attracted much attention, espe- cially in regard to a controversy on the subject of glaciers. Regelation takes place between blocks of ice where they are strongly pressed together, even in warm water, and in cold water it will take place when the masses only touch each other. When fragments of ice are subjected to pressure in a mould, they may be formed into a solid block. When but little
