Q. What is the cause of snow?
A. When the air is nearly saturated with vapour, and condensed by a current of air below freezing point, some of the vapour is squeezed out, and frozen into snow.
A few years ago, some fishermen (who wintered at Nova-Zembla), after they had been shut up in a hut for several days, opened the window, and the cold external air rushing in, instantly condensed the air of the hut, and the vapour (which was squeezed out) fell on the floor in a shower of snow.
Q. Why does snow fall in winter time?
A. Because the sun’s rays are too oblique to heat the surface of the earth; and (as the earth has no heat to radiate into the air) the air is very cold.
Q. What is sleet?
A. When flakes of snow (in their descent) pass through a bed of air above freezing point, they melt; and fall to the earth as half-melted snow or sleet.
Q. What is the use of snow?
A. To keep the earth warm, and to nourish it.
Q. How can snow keep the earth warm?