, 1892-10-26

Astronomy. which some years back seemed
to be yielding in interest to the sciences
which concern themselves with things terres-
trial. has Of late again come to the front and
is again attracting the attention of the entire
intellectual world. This is not 80 much from
Improvements in the mathematical depart
ment Of the subject as from improvements
and additions to the means of observation.
A great English astronomer was able, a year
ago, to explain to q large assembly Of the
followers and admin rs Of science, how it
was possible, by the aid of the spectroscope,
not only to show that some of the so-called
fixed stars are moving away from us and
others approaching US, but also to show at
what rate this movement was going on
in each case. By the same wonderful in
strument it has been shown that a certain
star approaches US during "a hours and then
recedes from us for the same period, and,
what is Atill more striking, the telescope
shows that the light of this star is some
times obscured as though the star were par
TALLY ecIipsed. The two observations taken
together appear to prove that we have here
a brilliant sun and a dark (~extinct) sun
revolving about each other, the revolution
being completed in 68 hours. 1t is not only
by the speotroscope, howeve. that the means
at the disposal of the astronomer have been
enriched. Photography has also revealed to
us many wonders, not the least of them being
this, that there are stars in the heavens
which the eye never sees, but which make
their influence felt on the sensitive plate.
Another great aid to the celestial science has
been the large telescope of the Lick Obser-
vatory Of California, erected, as everybody
knows, by the wealth of a successful
Californian miner 1t is to this fine instru-
ment that we owe the last great astronomj-
cal discovery, namely Of a fifth satellite is
Jupiter. Most people know Jupiter and his
four moons. The planet himself Is just now
visible here every night, rising about sunset.
A fairly good b~inocular will show the moons.
that ia the four moons, for the fifth is so
NAL that it has taken the finest glass" in
the world to discover it, and its existence
gas never suspected until August Of the
present year, when it was detected by Pro
fessor Barnard of the Lick Observatory. A
writer in Nature says that It's distance from
the centre of the planet lie 1870 miles. and
its period Of revolution II hours Sc inmates.
In the latter figures there may be some typo
graphical errors, for in the Men, York World
Of the 18th instant. we fnd a notice printed
below of the confirmation of the discovery
by another observer, at Princeton, and in
this notice the period Of revolution is said to
have been first stated as II hours and 50
minutes, but has been later corrected to Ii
hours IS minutes aud 80 seconds. The dis
tance from The planet is small. Jupiter has
a diamete equal to about eight times That of
our earth. say $4,000 miles. 1t follows that
the distance between the surface of the
planet and the newly discovered satellite
IS less than once the diameter of the
planet; and it is no doubt this nearness
to the bright surface of the planet which has
prevented it's earlier discovery. The writer
in Mature before referred to, says, it is
perhaps rather singular that it WAS not
detected by the shadow, which would be
projected on the disc Of Jupiter whenever the
satellite passed between the planet and the
sun, which is of daily occurrence. At such a
time the shadow would be seen as q small,
black, circular spot moving rapidly from
east to west across the disc, and with great
sr apparent velocity than the visible mark
ings on the disc of the planet. By way of
explanation the same writer adds, that it is
quite possible that the shadow has been
observed on more than one occasion, but
mistaken for an ordinary spot on the surface
of Jupiter.
The discovery is a very striking one, and
we cannot wonder that. according to the tels-