What is ice?
Ice is water in a solid state. Under ordinary conditions, water changes to ice at 32 °F. and 0 °C. In freezing, the molecules arrange themselves in hexagonal crystals, as may be seen by the examination of a snowflake. When exposed to the heat of the sun, ice not infrequently falls into six-sided needles or columns. One hundred volumes of water make 109 volumes of ice. Ice is lighter than water and floats, therefore, on its surface, protecting ponds and lakes from being frozen to a greater depth. Ice is far from being rigid. In fact, it is so fluid-like that on the slopes of mountains it runs down slowly, forming oftentimes enormous streams of ice, called glaciers. If a long slab of ice be supported at the two ends, the center will curve downward. A slight jar facilitates the formation of ice. If perfectly quiet, water will cool several degrees below the freezing point without solidifying; but a jar, which, no doubt, facilitates the rearrangement of the molecules, will turn it suddenly into ice. Under pressure sufficient to prevent expansion, water may be cooled far below the freezing point and yet remain a liquid. Sea-water freezes at about 32 °F. The ice in some way drives down or excludes nearly all of the salt. The people of the Mediterranean early learned the use of ice in cool-in drinks. They depended largely, however, on snow brought from the Alps and other mountain peaks.
