By the nature of our atmosphere, we are protected from the influence
of the full flood of solar heat. The absorption of caloric by the air
has been calculated at about one-fifth of the whole in passing through
a column of 6000 feet, estimated near the earth’s surface. And we are
enabled, knowing the increasing rarity of the upper regions of our
gaseous envelope, in which the absorption is constantly diminishing,
to prove that _about one-third of the solar heat is lost_ by vertical
transmission through the whole extent of our atmosphere.--_J. D.
Forbes, F.R.S._; _Bakerian Lecture_, 1842.