New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1850-12-07
MOVEMENTS OF FIXED STARS ::
A LECTURE.
BY PROF ON. michel. OF CINCINNATI
fps,,,,,s4 for The 7'yTbgse1

REPORTED for he ITT5aHel
Notwithstanc;ar the severity Of the vyentee7 %
Thursday evening, the Chapel OF the Female
Academy in BROOKLYN was neariy filed. large
proportion OF the audience being ladies', who had
braved the storm 70 listen to Prof MitcheIs last
lecture After expressing h;s qualification At see
ing so many together, the lecturer announced his
intention to Introduce lis hearers to topics upon
the confines OF the certain and the uncertain
There were all degrees Of certainty, from the
broad sunshine Of truth TO the dim twilight Of
doubt Il e spoke OF the degree of accuracy which
has been attained in relation to the Interesting
problems of the solar system and Of those points
on which there is still doubt and which can only
be cleared up by the possession of more tail and
accurate data on which to base calculations
These data relate to the distances, weight and
direction of the planetary bodies, all Of which are
to be ascertaiued with precision, instead Of APP
rroximsrely, as at present. On enc other cues
tiou connected with this system, there IS still
great doubt. The sun rotates on It's axis, but It's
period Of rotation is uncertain since it can only
lie marked by sJs5tS which are not stationary upon
its surface. It theF were Ike the MOUNTAINS ct
the moon, or the spots ou the planets, It's period
could be exactly known. and much light thus
thrown upon tire uebular hypothesis. But when
we pass beyond the limits Of the planetary system
With winch we are connected, we at once pass INTO
the region Of doubt. But few years ago nothing
whatever was kuawp OF any OF laws or pheno
meua to be found among the liked stars lie
Gently something has been been learned and
some fzw facts established relative to these dis
taIt bodies. The speaker cautioned his hearers
against surprising from the tew brilliant discOy-
cries which float upon the surface OF science, that
ali was clear and determined in relation to the
stellar system though these discoveries all
true. in degree. In one instance the parallax
Of fixed star has been determined. TINS para
lax the speaker explained as the apparent change
OF position OF the observer II this could be &C
cUraey observed, the stars would appear t. de-
scribe minute Circleso the same form the earth
orbit. But there are many and serious diihcu
ties in the way OF ascertalning this circle The
instruments are imperfect, and the alteration OF
light caused by its own motive and the motion OF
the earth, give apparent motion to each OF the
stars. Bat when these false motions are calCula-
ted aud deducted from the observed motion OF the
star there is still a resIduum OF motion remain
ing in one instance,-the double star oil in the
Swan. The resiiuum Of motion can only be CHAR
ged to the parallax and it is SO small that the dl-
8meter of the whole circle described by the star
is only one six thousantth part OF the suns aPpa'
rent diameter. This observation which was made
by Bessel some wears since, has within eighteen
months been fully confirmed by Struve, at the
great Imperial Observatory at Puttowa Thus
Observatory was built by order OF the Car who
gave Struve cdrfebldnche directing HIM toprocure
the best instrument the world could afford aud
make an observatory which should be as sun
among all the others on the earth. The distance
to this star was thus determined 1t was found to
be double or n system of two stars revolving
around common center IN n period OF i've nun
bred wears they were weighed and Doth TO-
gether found not to amount to onethlrd the mass
OF the Sun. The star Alpha in the Centaur, and
.4lpka in the Tyre had also been found to have
parallectic motion The star numbered 1880 IN
the catalogue Of Broombrdde, it was announced
bv the French astronomers, had parallactc mo-
ton which would indicate that it was nearer
than any other fixed star. But Strive had
investigated it till he was satisfied that no
parallex at all could be discovered. Thus we
seemed to be retrogading instead OF advancing IN
our knowledge of these subjects but 1t was be,
cause the investigations were IN the regions OF
uncertainty. w must wait and work collecting
data and establish little by little minor iacts before
we can claim to know with assurance the distance
of the fixed stars There is q remarkable class,
called variable stars which periodically lose and
regain their light. One called Algol III the head
of Medusa has been observed for go years. 1t
has period of two days and twenty hours, two
DAYS and thirteen and half hours of winch It
shines as a star of the first magnitude, then
suddenly loses nearly all its light, and for
short time is nearly or quite Invisible
But beside this periodic dininuton Of light it is
found that its periodic time is diminishing. This
the speaker thought it possible TO explain by sup
posing an OPAQUE body to be revolving round the
star whose orbit was gradually contracting as
that OF the earth is now changing. Another star
has period Of 3}l days. Another star IN the
Southern hemis phere is most extraordinary. rita
OF the constellation Argus was observed as early
as 900 to be luctuatiug in its brilliancy In 1913
Herschen observed it rapidly closing up aud rival
ina hrchrnpeS and thpD tUPtuntlDp
pareUty without law or order theological
facts seem to Indicate that such changes
NAV have at some period taken place in the sun,
but the explanation Of the phenomena is beyond
the power of men. Possibly after the observation
OF many years the changes may be found to con
form to a regular order. Stars have flashed up
and disappeared again. The Professor had Oh
served such an one Tycho saw one in 1872.
One was seen 3l2 years before that time and one
nearly in the spot 3l2 years before that
extend to the fixed starsi Does grayitation at
feet them? This is field which has been recent
~ opened and is now being carefully cultivated.
Herschel in his endeayors 70 determine the para
lex sought to find two stars, one which should be
exactly behind the other, TO make his observations
upon. Heeaned that some ofthem were physical
~ united. This announcement attracted the atten-
ton of the first Astronomers and assutticent
data were collected the fact was found 10 be prov
ed. The orbits of one hundred and thirty binary
stars have been defined and computed. Their or
bits are in all planes, some OF them in a line with
the eye, so that they seem to be moving in line
back and forth; others in plane parallel to that
fthe earths orbit, so that they move in an appar
ant circle now changing the distance from one an
other, and the remainder move in planes, at all the
Intermediate angles of inclination. But while
they are rotating around each other, these, as well
as the other fixed stars seem to be moving together
through space at all the grades of speed. This is
called the UrOUer motion OF the stars. Sir w H.
liam Herschel conceived that it might be explain.
ed by supposing that the sun was moving among
them, aud this theory which caused great aston
ishment at the time has more recently been taken
up and it is found that notwithstanding the posi-
bilities Of instrumental errors, the possibilities