The National tribune. [volume] (Washington, D.C.) 1877-1917, 1891-12-17
THE WEATHER.
A Talk tbOut the Color Of tn. ssy.
BY LIEUT.. }. p. FINLEY. u q. SIGNAL sERvIc


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This subject has received much consideration
\ by philosophers from the time Of Newton To the
present day. Even pri0r,to Newton no little
attention bad been given the matter. The hy-
pothesis Of Newton comes very close to the ex-
pcrimental results of to-day. He gave IL as his
opinion that the blue color Of the sky was due
10 the extreme fneness Of the PARTICLES which
reflected the sunlight. This would apply to all
vapors, and especially the vapor of water before
condensation had progressed sufficiently to
form clouds rejecting other colOrs. And so.
this 1.-THE bluel being the first color which va.
pOrs begin TO reflect. IL ought 10 be the color Of
the finest and most transparent skies, in which
vapOrs are not arrived TO that grOssness requi-
site TO reflect other colors. The opinion of
Newton has been verified by Prof. Tyndall,
after a lapse of nearly 200 years
Some OF the earliest writers considered the
blueRess of the sky as simply the effect upon
the eye of looking into the infnity of space.
Others insisted upon an actual blue color Of the
air. Others again, that the blue color was an
optical illusion. Even Sir David Brewster
seems 10 have had doubts as to the reality of the
sky's bneness.
Several years before the appearance of Prof.
JyndaHs celebrated paper, Prof. Clausus, of
Bonn, accepting Newton's idea, investigated the
conditions necessary TO the production Of the
blue color. He found that the rejecting me-
dunn cannot consist Of solid drops as Newton
may have imagined, but must be composed of
bubbles the films Of which do not exceed in
thickness quarter Of the wave-length Of viO-
let light. He proceeds 20 prove that the blue
color must occur only under atmospheric con-
TFrnF 81 q
lielmholtz practically accepted this view when
he states that 1.-THE light reflected by the ether
pervading the universe is bluer the finer the
PARTICLES, while cOaTser particles reflect all
c0l0rs and give white effect. Such Is the blue
OF tho heavens-that is 20 say, of the atmos-
phere-seen against the blackness of open space.
The purer and more transparent the air, the
bluer are the skies"
The results OF later investigation through tho
aid Of spectrum analysis seem to show that
by means of popularity Of the human eye the
impression OF color il the effect of certain de-
grees Of intensity Of light upon three sets OF
nerve-termini in the eye. One Of these sets is
influenced by red light, another by green, and
another 1.-THE weakestl by violet or blue rays.
Upon this popularity OF the eve depend all
those striking changes Of hue due TO variations
OF the intensity Of illumination, says DIR.
Nichols Passing cloud shadows on the water
at monday reveal an indigo-blue, which in
siantly becomes a silver-gray in the direct sun
light. Daylight IS simply the light Of tho sun
weakened by manifold difuse reflections. In
general white light will seem blues and bluer
as Is intensity diminishes, and this law will
apply to the skies. As the light they reflect
hecomes fainter and fainter. they will increase
IN blueness, even though the light, by the proc
ess OF rejection, suffers no change in cOmpO-
stion. As the general intensity Of the light
diminishes the rays seem bluer and bluer.
There is still a contest Of opinion between
those who hold TO the influence Of tho human
eye In explaining the character Of the blue
color OF the sky. and those who give greater
weight to the vapors OF the atmosphere. The
solution Of this problem is not likely to have
much influence on weather forecasting.