Evening star., 1895-05-25

tunately the rest OF the description is not
true to nature. The maiden's lovely
tresses' cannot be seen, nor her snowy
feet" nor even her ''all glorious" eyes.
Virgo is, in fact, one of those mystifying
consultations of which the origin is lost
in an antiquity so remote that their ra-
tionale is no longer recoverable. The con-
stellation certainly did not originate as
many of the consultations undoubtedly did,
IN any SuSgeStiveneSS in the grouping of
the stars. Indeed. so vaguely defined were
its limits in the time of Ptolemy that this
astronomer did not hesitate to remodel it
for the sake of giving the figure better
proportions"
Virgo is one of the zodiacal conste.la
tons, the sixth. reckoning from Aries but
the seventh if we reckon from the present
position of the vernal equinox at the begin
ming of the constellation Pisces. 1t occu-
pies the place of the Sign" Librae which
the sun enters about the 21st of Septem-
Der. The autumual equinox-the point at
which the sun crosses the celestial equator,
in passing on the date just given. from the
northern to the southern hemisphere-is at
about two-ffths of the distance from Spica
to Regulus, in Leo, almost exactly on a
straight line drawn from the former to the
latter star.
In the time of Hipparchus, in the second
century B. C.. Spica was in the northern
hemisphere 1t is now in the southern
hemisphere. being a trifle over ten degrees
south of the equinoctial or celestial eaua-
tor. The change has been brought about
not by any change in the stars position
with reference to the surrounding stars
for all of the stars have been similarly af-
fected. but by change in the location of
the line which divides the two hemispheres.
The celestial equa tor is the great circle in
which the plane of the earth's equator, in
definitely extended on all Sides cuts the
starry sphere. Since the earth in its an
nual passage around the sun has a very
slight gyratory mouon-a motion which
has been compared to the wabblng of
spinning top-the plane of its equator and
consequently the line in which this plane
cuts the celestial sphere are continually
changing their positions. The two points
at which the celestial equator and the
eclptic, or suns path, cross each other are
slipping to the westward at a rate which
in the last 1000 years has changed their
positions among the stars some thirty de-
grees-the length of a zodiacal ''sign"-and
will carry them completely around the
heavens. The discovery of this movement,
known as the procession of the eQui-
noxes," one of the first grand discoveries
of mathematical astronomy, was made by
Hipparchus by means of this very STAR
Spica. Hipparchus found, upon comparing
his own observations with those made one
hundred and fifty years earlier that the
star was somo two desrees-four times the
diameter of the moon-farther to the east
than his predecessors had placed it, and
since it's position remained unaltered with
respect to the neighboring stars, it became
evident that a change had taken place in
the point-the equinox-from which the
measurements We're taken.
This continual change in the position Of
the equinoXeS has very important bear
ing in modern astronomy. The positions of
the celestial bodies are given in star cata-
logues, or laid down upon charts, by right
ascensions" and "declination," which cor
respond to longitude and latitude in ter
restrial geography. Right ascension Qongi-
tude) is reckoned eastward from the vernal