If Small Clouds Increase Much Rain

THIS and the following Observation cannot well be understood, without

giving some Account of Clouds in general. The Atmosphere is supposed to

extend itself about five Miles round this Globe of Earth, and within

that Space move all kind of Vapours exhaled by the Sun's Force, or

protruded by the subterraneous Heat. The ascending of these Vapours

into the Air, depends upon many things, and therefore as different as

its Ca
ses; for instance, their ascent depends in the first place on

the degree of Heat with which they are drawn up or forced out; next

upon the Lightness of the Vapours themselves; thirdly, on the Density

or Rarity of the Air through which they pass; and lastly, on the Force

and Direction of the Winds, which they encounter in their Passage.

ACCORDING to the Nature of these Vapours, and the Circumstance

attending their Passage, they appear to us differently below. For if

they be extremely subtile they mount very high, and there, according to

the Sentiment of Sir Isaac Newton, form by Refraction the Azure, or

blue Colour, that over-spreads the Sky in serene Weather. Clouds, while

they remain visible, do not rise above the Height of a Mile; and we

always observe, that the highest are of a very light Colour, and hardly

seen. If, therefore, small Clouds increase, it shews, that the

Disposition of the Air is such, as that these Clouds cannot rise

therein, either from their own Weight, the want of a protrusive Force,

or from the falling of the Wind, which in cloudy Weather is always a

Sign of Rain.