Because, in the act of congealation a great deal of heat is given out, and taken up by the air, and thus the severity of the cold is in some degree moderated.
164. Why is it frequently colder when a thaw takes place?
Because, in the process of thawing, a certain amount of heat is withdrawn from the air, and enters the thawed ice.
165. What benefit results from these provisions of Nature?
They moderate both the severity of frosts, and the rapidity of thaws, which, in changeable climates, would be seriously detrimental to life, and to vegetation.
166. Why are furs and woollens worn in the winter?
Because, being non-conductors, they prevent the warmth of the body from being taken up by the cold air.
167. Why are the skins of animals usually covered with fur, hair, wool, or feathers?
Because their coverings, being non-conductors of heat, preserve the warmth of the bodies of the animals.