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.