Fine weather When the sky is grey in the morning.
Wind When the sky at sunset is of a _bright_ yellow.
Rain When the sky at sunset is of a _pale_ yellow.
Wind and rain When the sky is orange or copper colour.
Fine weather When the sky has light, delicate, quiet tints and soft, indefinite forms of clouds.
Rain and wind When the sky has gaudy, unusual hues, with hard, definite outlined clouds.
Fair weather When sea-birds fly out early and far to seaward.
Stormy weather When sea-birds hang about the land, or fly inland.
Fair weather When dew is deposited. Its formation never _begins_ under an overcast sky, or when there is much wind.
Rain On what is called a good _hearing_ day.
Rain When remarkable clearness of atmosphere, especially near the horizon, exists, distant objects, objects, such as hills, being unusually visible or well defined.
The atmosphere at a given temperature is capable of retaining only a given quantity of aqueous vapour, invisibly diffused through it, at which temperature it is said to be _saturated_. Should the temperature from any cause be lowered, the aqueous vapour at once becomes visible in the form of either cloud, dew, rain, snow, or hail. It has already been shown that, although marshes and rivers, inland seas and lakes, yield by evaporation watery vapours to the air, the ocean is the great source of rain, whence it is lifted in vast quantities by the sun’s radiant heat, to be subsequently condensed by passing into cooler regions, or by contact with cold mountain peaks, falling to earth as a fertilizing shower or a devastating flood.
Sir John Herschel accounts for the formation of raindrops by saying:—“In whatever part of a cloud the original ascensional movement of the vapour ceases, the elementary globules of which it consists being abandoned to the action of gravity, begin to fall. The larger globules fall fastest, and if (as must happen) they overtake the slower ones, they incorporate, and the diameter being thereby increased, the descent grows more rapid, and the encounters more frequent, till at length the globule emerges from the lower surface of the cloud at the ‘vapour plane’ as a drop of rain, the size of the drops depending on the thickness of the cloud stratum and its density.”