[AS. is, isa.] Water freezes into ice when its temperature falls to the freezing-point, which is 320 on the Fahrenheit thermometer, and zero on the Centigrade. Ice forms on the surface of water, which expands in freezing - that is, any given quantity of water makes a larger volume of ice. The ice is therefore. lighter than water, and this is the reason it floats. The expansion of water by freezing produces very remarkable effects on rocks and stones, splitting the rocks open and cracking the stones. Ice is found all the year round in the Polar regions, and on the tops of very high mountains. Glaciers are vast bodies of compressed snow and ice which move slowly down mountain sides. Icebergs are large masses which break away from glaciers on the Arctic coasts, and, falling into the water, float into warmer seas. Ice is now an important article of commerce, and is shipped in large quantities to warm countries, chiefly from the United States. Norway sends ice to Great Britain. Large quantities of ice are now made by freezing machines, in which cold is produced by chemical action.