1911 Encyclopædia Britannica/Snow

SNOW (in O. Eng. snáw; a common Indo-European word; cf. in Teutonic languages, Ger. Schnee, Du. sneeuw; in Slavonic snieg’, Lith. snëgas; Gr. νίφα, Lat. nix, nivis, whence the Romanic forms, Ital. neve, Fr. neige, &c.; Ir. and Gael. sneachd; the original sense of the root may be to moisten, cf. Skt. sneha, moisture), that form of precipitation of water-vapour condensed from the atmosphere which reaches the ground in a frozen and crystalline condition. Snow thus occurs when the processes of condensation and fall take place at a temperature below 32° F. The crystals, which vary greatly in form, belong to the hexagonal system. They are formed upon a nucleus, in the same way as a raindrop, and sometimes reach the ground singly, but more commonly in small coherent masses or flakes. If in its passage from the upper atmosphere snow passes through a temperature above 32° F. it reaches the ground as sleet or rain (according to the degree of heat encountered), and thus after a fall of rain over lowlands, the higher parts of mountains in the vicinity may be seen to have received the fall as snow.

See further Climate and Meteorology; and for the transformation of snow into ice under pressure, see Glacier.