Evening star. [volume] (Washington, D.C.) 1854-1972, 1896-06-06

across the who'll. southwestern quarter of
the heavens. its head being low III the west
and the tip OF its tail being a a scrlew hat
greater altitude almost exactly on the
meridian. The Serpent proper. together
with OPhiUchus. the Serpent Holder, occu-
pies the greater portion Of the southeastern
quarter Of the heavens, and in the north,
now a nearly its greatest altitude, above
and to the right Of ths pole star. may be
seen The great Dragon.
The scarcity of celestial serpents is per-
haps due 10 the fact that the imagination
Of the ancient star-gazers required, as it
would seem. that a serpent should have
not merely a snaky body, but also a suit
able head. At any rate. the heads of these
serpents are the parts Of them the most
easy TO make out. The Fydrds head is
formed by n short curved line Of three
stars, Of which the central one is the
brightest, and may pass very well for an
eye, as II probably dId in ancient times.
The head of the Serpent consists of a small
triangle Of stars, Of which TWO of the third
magnitude make an excellent pair Of eyes,
while the third of the fourth magnitude
Is in its hose. or, perhaps. its tongue. This
head Will be found tonight at the hour
named a short distance below and to the
right of the Northern Crown. Still more
strongly marked is the head of the Dragon.
1t consists-at least as 1t is now represent
ed on the chariot trapezium of four
stars. two, the eyes. of the second mag
nituIe, one of the third and one of the
fourth.
1t is curious that these quite obvious
points in the makeup Of these Constelia
lions have been entirely disregarded by
the artists who have drawn their figures
for our modern charts. In none of the
feuciful and usually hideous heads which
they have Depicted have the eyes been
Dragon this is particularly remarkable,
since the monsters fierce" (torvD, or
flaming (ardentes) eyes are repeatedly
referred 70 by ancient writer's
History of Discovery.
One Of these eyes of the Dragon-the
lower, as we now see them, which is
known as Gamma Draconis-has a quite
prominent place In the history of astron-
omy. 1t was from observations of this
star, made with the hope of determining
its paraIIax, that Bradley discovered the
alteration of light Perhaps 1t should be
stated here what is meant by stellar
parallaX-" 1t is that Very slight annual
shift of the position of a star due to the
movement of the earth in Its orbit, in con-
sequence of which our point of view as
We observe the stars is shifted semi-an-
nUaiy to the extent of 1SJ,tso,pbO miles
the diameter of the earth's orbit. This
movement of ours causes the stars to APP
pear to describe on the face of the sky
minute ellipses, which, as can easily he
shown, will have exactly the form and
size WnIcn the eaFjE ; oTDlI "OuIu nave,
seen from the stars. The Gliipse will, there
fore, be smaller. OF course, the farther the
star is away, and where 1t can be meas
ured 1t affords Il means of calculating the
stars distance. SO minute. however. is this
stellar displacement that only in the cases
OF the very nearest stars has II been found
possible to detect. much less to measure, 1t
with the most refined of modern appliances.
Bradley discovered, as he had hoped to
do, that, as the earth SWUNG around on its
annual circuit, Gamma DracOniS described
a little ellipse in the heavens, but he was
perDleXed to find that the stars movement
was not precisely what it should be If it
We're due to parallaX. The star moved in
the right direction, but it was continually
one-quarter of 4 revolution in its little path
behind the point at which il ought to be.
Here Was something that called for an en-
PLANTATION and Bradley hit upon the true
one. which IS this: Light does not come
from star instantaueOusly, but occupies
in It's passage an appreciable time. As We
now know, Il travels al the rate of 1856 90
miles second. This fact. taken in connec-
ton with The earth's rapid movement
eighteen miles second-explains complete
y what Bradley saw. The effect OF the
CompOunding OF these two movenients-that
of light and that of the earth-rnay be il
Illustrated by tho case of rain.
Suppose shower TO occur at time when
the air is perfectly quiet. The drops fall
perpendtcularly, and person wearing
broadbrimmed, Waterproof hat may stand in
the shower and be completely sheltered.
buA !Sl nun start 10 run IN any QlreCtlOn,
and the rain Will beat against his face.
He runs against the falling drops and the
effect is the same as though the drops
were driven against him in q standing di-
rection by wind So it is with light.
A Necessary Correction.
To illustrate by a special case, the earth
Is now situated very nearly in a straight
line with the sun and the star Antares. in
the Scorpion. which We may see low in the
southeast. That is. an observer on the sun
would see the planet earth very near this
star. We are therefore now moving at
right angles to the direction in which the
light comes to US from Antares-noving to-
ward the east. The light of the star. there
fore. strikes US in the face, SO to say. keep
ing up the analogy with rain; we run
against II in such way that 1t seems to
coms to US from point a little to the east
Of that from which II actually does come.
A. consequence. the star Is seen little
TO the east Of Its true position.
since we are always in motion, the star