Professor Dove of Berlin relates, in illustration of the formation of
clouds of Snow over plains situated at a distance from the cooling
summits of mountains, that on one occasion a large company had gathered
in a ballroom in Sweden. It was one of those icy starlight nights
which in that country are so aptly called “iron nights.” The weather
was clear and cold, and the ballroom was clear and warm; and the heat
was so great, that several ladies fainted. An officer present tried to
open a window; but it was frozen fast to the sill. As a last resort, he
broke a pane of glass; the cold air rushed in, and it _snowed in the
room_. A minute before all was clear; but the warm air of the room had
sustained an amount of moisture in a transparent condition which it was
not able to maintain when mixed with the colder air from without. The
vapour was first condensed, and then frozen.