The Cairo bulletin. (Cairo, Ill.) 1???-1928, 1904-11-08
BLUE COLOR OF HEAVENS.
Explanation of Savants Continues to
Be Much Disputed.


The blue color of the heavens is a
subject which Prof Spring of the
Liege University recently treated in a
conference before the Swiss Natural
Science societies during the late con
gress. He classes the explanations
which sayants have given up to the
present as to the blue color of the
heavens in two categories. The ply
steal type Is based mainly upon the
experiments OF Tyndall regarding the
illumination of vapors. The chemi-
cal type is the more recent. and Is
based on the actual color of the at
mospheric components. The former
experiments which led to the physical
theories of the blue color seem to
have been borne ont by the recent ex-
Derments of Rayleign upon the refec-
ion of light by the particles of
roubled medium, and these are found
o reflect great number of rays of
short waye-length This causes such
a medium TO appear red by the trans
)arence and blue by reflected light
Besides, the plane OF polarization has
the same direction as in Tyndall's eN
periments. Mr. Spring, however alb
serbs all the blue light from the heav-
ems by means of an appropriate alb
sorbent medium, and thus observes
that the polarization of the light in
the beam is not a sufficient proof of
The optical origin of the blue color
since it Is demonstrated that other
wave-lengths are polarized The objec-
tons to Rayleigh's theory which are
made by Pernter of Vienna, strength.
N his view; Royleigh's theory would
lead us to predict violet color, rath.
n than a blue for the heavens. Be
sides, the dust particles Of all kinds
which the atmosphere contains do moi
rise to a height of over 5000 TO G,000
feet, and the action of gravity and
also the electric state of the atmos-
phere tend to precipitate them. The
question arises whether It is the
molecules of the gas itself which pro-
luce the solar reflection. This seems
be denied by l.. Sorets expert
nents, which prove that his hypothc-
SIS does not hold good for liquids or
solids, and more recently the author
finds negative results in the case Of
gaseous particles. Hagenbach cz.
plains the illumination of the atmos-
phere by attributing it to a series of
layers of different densities which
cross and intermingle. thus causing
reflection and refraction of the Hight
rays The author considers that such
a theory would be satisfactory To ac-
count for the illumination but cannot
be used by the partisans Of the ply
sical theory TO explain the color of the
heavens. In fact il accords very well
with the chemical theory OF the blue
color The author then made series
of original experiments to prove that
a troubled medium will only seem
blue to an observer who is plunged ia
it. in case the medium itself possesses
a blue celebration. In the case Of the
atmosphere. the author uphOlds the
theory OF an inherent blue color by
his calculation that the oxygen con
tanned in the air, leaving out the pos |
sible effect Of ozone, Is sufficient 10
give the medium a deep enough color
to explain It's actual appearance and
the variations we find in the different
directions oi sight. These calcula.
lions are based upon the liquid state
of the gas. The dust PARTICLES. IN
stead OF being the cause Of the blue
color. only have the ofec; Of ohstruct /
ing il to a greater or less extent and I.
thus cause the variations which are
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