Evening star. [volume] (Washington, D.C.) 1854-1972, 1910-07-26

latitude 6f degrees and thirty-two min
utes north: while on October first, at
second orbital quadrature, the north poe
Of meridian sunlight again coipcldes WIN
the north geographical pole. IN other
words. the north pole of meridian sun
light describes a series of expanding ana
contracting spirals, as shown eiseWhere
in the so-called Naulty curve, with Gull
minating points as indicated.
The motion of the earth on its axis SUD
jects the auroras and the zooiacal nsn ai
to differing conditions. The equatorla,
line Of light which causes the zoolacai
light is merely reflected and so SHOWS III
tie change in color; the north pole OF the
meridian line of light. when 1t comes IN
contact with the pole of earth's motloh.
is defracted, not only by the motion OF
the surface of the earth at the geograph,
ical pole but also by the VortexlcaI alu
vertexical motion of the earths athlos
phere at the pole and In the arcuc
gions. What happens Is that the extern
sion of the meridian line OF sunlight, DC
tween its pole on the earth's SURFACE anu
the limits of the atmosphere surrounu.iis
the polar regions, Is defracted ny sns
spinning motion of the earth anu -
snread out in fanlike radiance OF PITS
matte colors. The arches OF SOHO coioi
which run athwart the rays are the ~, -,
Illumination OF layers or atmospIe,e
differing density, and their color VIII us
close the density OF eacn layeI. ~, .
rlace of origin and the place OF oose .i,,ii
tion. explains other appearances "nie
the mysterious dark curtain uioes ~. ~
aurora is merely the dark arc g
,rosnb,re between the observer anu the
nlace of origin of the aurora. rms Is
proven by the fact that the fartner away
the observer is the greater tnat udth ~ -
tain appears, while, as Sir ernest Sma
Teton told me this spring, II the JUS tne
he near or at the point of contact or tne
mole of meridian light with the earn d;se
p ors the dark curtain" wholly ols-
appears.
Not on Magnetic Meridian.
Close observation will show to any
one that the major axis OF either NC
nortbern or southern auroras does not
10 in tho magnetic meridian at all times.
IT,. ,.ria+ion Is pronounced at times. ana
this variation always agrees with the
factors Of place of origin and obesrva-
tion already described. A few experiments
with data OF aGrOral observation sonar
declination and an ordinary terrestrial
globe will show many connrmatlohs VI
tie facts herein SEE forth. In simphctS
rhe zodiacaf light is the solar equatorial
illumination of the earth's atmosphere.
changing place with the declinatlon OF the
SUM- observed from the dark SIDE OF tne
earth and non-prismatic because not sub
iectcd to refraction by motion: and the
auroras are the polar parts of the merid-
ian line of solar illumination OF the
aarrh's atmosphere, changing place with
the II declination Of the sun. reaching
maximum manifestation at coincidence
with the poles of motion of the earth and
with the magnetic poles. and prlsmatic
because subjected to the revolution, In
small area, of the earth's surface and
the polar atmosphere.
The zodiacal light furnishes certain
means of measuring the height to which
the dense atmosphere Of the earth ex-
tends. by using its width at the horizon
as base line This method has been
adopted many times by the writer.