Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1917-12-16

tnctly. Is this unusual, and what is Its sicnib
canccT Mrs 7 >r
What you a very beautiful lunar
halo phenomenon rarely exhibited with so
much perfection In this latitude. Although tho
coiors YOU observed were those of the rain
bon. Yet II was not IA roinbow. n YOU had
taken particular notice Of the arrangement Of
the prismatic colors In the circle. you would
have seen that the red was inside whereas in
the RAINBOW the red is outside. True lunar
rainbows do occasionally appear but. like rain
bows formed by the sun. they only visible
in the part Of the Sky opposite to the moon that
is. the spectators back must be toward the
moon Cor the SUM. Their colors tho same
as those OF solar ranbows because moonlight
is nothing but reelected sunlight. but they arc
comparatively faint because the Intensity Of
moonlight is SO much less than that Of direct
sunliEhr.
a rainbow never shows complete circle, but
at the most only Semicircle. unless the OBJ
server happens to be a great elevation as
in balloon. when more than half Il circle can
be seen. but never entire Halos and
rainbows also differ in the size of tho circles
or Senlicircl"s that they exhibit. The radius
OF halo is about 90 degrees and that OF a
rainbow about 4: degrees. Other arches and
circles are sometimes outside Of both the
rainbow aud the halo. hut the radli given arc
'or I'll" principal or primary. phenomena.
Another Fundamental difference between a
rainbow and halo is that the OF tho
former is 81 combna ton of the effects of refrac-
ing raindrops. situated in the opposite par, of
the sky from the sun or che moon while 4 halo
is caused simply by refraction of light passing
through of floating ice crystals in the
same quarter Of tho sky where the sun or the
moon is. In order to have a halo 1t is only
necessary that the light should BIO turned out
OF ita course (rrtracted) at a certain angular
distance tabout ~ degrees As degrees for a
secondary halo) from the luminous body by
pr!Smatc particles OF ice in the upper ai".
which. while turning the light from it's original
direction. and thus bring ing it to the observers
eye. at the same time dispense the primary
colors into colored band.
But have a rainbow the light must first
enter drops OF liquid water falling in shower
and be there retracted have It's primary
coiors dispersed by the and then be re-
fccted from tho inner surface OF the drops on
the side opposite TO tho sun. and thus be sent
back 10 the Observers eye. which is situated
between the falling drops and the sun. In the
reflection from the back of the drops the order
OF the colors is reversed and the comes out
below and this causes the upper or outer Dor
der OF the rainbow 10 appear red. because il the
red ray from particular drop the
the other colored rays will pass above the line
OF vision. but a violet ray from n lower drop
will enter The eye the same time as the red
ray from the upper drop. and thus tho bow
appears red above and violet below. There is
no similar reversal in the cOiors formed by
the passage OF the hight through atmospheric
ice crystals without reflection, and in the
halo the red is the inner and the violet on
the outer edge ofthe circle. Connected with the
halos are the amazing appearances called mock
suns which sometimes almost equal the real
sun in brightness.
There are many other magnificent phenomena
associated with the play Of sunlight and moon
light among the floating vapurs and crystals of
the atmosphere such the corona..
GIories that often appear around the
o. the moon when the air is filled with trans
lucen, clouds with extremely minute par
ticies OF water vapor. Like the halo the corona
10 formed in the Immediate neighborhood on.
and IS symmc; rcaNy disposed around. the luml-
nary whose light gives rise TO H.
But an entirely is in operation to
produce the corona. It is due TO neither rcfrac-
ton reelection. but d!nraction. OF light.
Difraciion is the spreading of Il OF light
iato the space behind obstacle that inter
rupts rs direct passage. The obstacles In the
case OF the formation of coronas the opaque
particles OF vapor. other substance, floating
in the air
One result of d!nraction s the dispersion Of
and from this arises the appearance of
prismatic hues in the ring OF corona about
the sun the moon. y be
distinguished from halo by the fact that its
colors are arranged the plan OF those Of
rainbow: i E, the rcd is at the outer border.
In addition TO all these. there the
dcrful phenomena OF "sunplars' anthelia
aerial specicrs. ''Uiloa circles" focbows. lumi-
nous atmospheric crosses and other strange
apparitions in the SKY.