SNOW

(Ger. schnee.) Congealed water, which falls from the bosom of the atmosphere. Very little is yet known respecting the formation of this meteor. It has not been ascertained,for instance, whether the clouds which produce it are composed of vesicular vapours, or of frozen particles; nor whether the flakes are completely formed before they begin to descend, or receive an increase in pa ing through the lower strata of the atmosphere. The temperature of the flakes, and the circumstances which determine their form and volume, are likewise unknown. The only observations which may be considered as in any degree complete, are with reference to the different forms which the flakes.a ume. This subject was considered by Kepler, Hooke, Ca ini, Muschenbroek, and many others; but the most interesting series of observations we po e are those of Scores by (Account of the Arctic Regions, 1820), who has reduced the different forms into cla es, and given a number of excellent representations of the flakes in different states. Generally speaking, when examined with the microscope they present modifications of stelliform and hexagonal crystals; and frequently they consist of n star of six rays formed of prisms united at angles of 60°, from which other prisms shoot at similar angles, giving the whole tin appearance of exquisite beauty and great regularity. The variety of modifications is probably owing to the state of the atmosphere when the snow is formed. If the crystallization takes place when the air is calm, the crystals will be regularly formed; on the contrary, they will be irregular and imperfect when the air is much agitated. Sometimes the flakes present no traces of crystallization. Snow is much le dense than ordinary ice. The bulk of a given weight of ice is only about a ninth part greater than that of the water from which it is formed, while the bulk of new-fallen snow is ten or twelve times-greater than that of the water obtained by melting it. At moderate elevations above the sea, and in the mean latitudes, snow most frequently falls after some days of pretty hard frost, and when the temperature of the air, though still a few degrees above the freezing point, is sensibly mitigated. On this circumstance is founded1133the remark [s. 1147]