Because, but for this, deep waters might be frozen through their whole depth. This would destroy the myriads of fish and other living things that inhabit the water. Parts of the earth, now clad in verdure, would be lost in eternal winter; and even in the most temperate zones it would take months to effect a thaw; and thawing would be attended with such floods and subterranean commotion as are terrible to contemplate.
344. Why are bed-room windows sometimes covered with crystalline forms on winter mornings?
Because the vapour of the breaths of the inmates has condensed upon the window-panes, and formed water. The water has frozen with the cold, and exhibits the beautiful crystalline forms into which its particles are arranged.
Here we have another domestic illustration of the great laws of nature. It is the same law which locks the arctic regions in ice and decorates our window-panes. This beautiful phenomenon is usually witnessed by us on frosty mornings when we rise from our beds. It has a story which the observer of nature may read in its sparkling eyes. It tells that, although without the air is biting cold, God has wrapped a mantle around the face of nature to keep it from injury; and that the earth and the waters, though looking chilled and dead, have still the warmth of life preserved in their bosoms.
Dew is watery vapour diffused in the air, condensed by coming in contact with bodies colder than the atmosphere.
346. Why does the air become charged with watery vapour?
Because, during the day, under the influence of the sun's rays, vapours are exhaled from all the moist and watery surfaces of the earth. These vapours are held in suspension in the atmosphere until, by a change in the temperature of the earth, and of bodies on the surface of the earth, they are condensed, and deposited in translucid drops.
347. What causes the decline of temperature that favours the deposition of dew?