The daily gazette., 1874-12-09
For the Gasette.
The Transit of Venus.

Between the time of the setting of
the sun this evening and its appearance
IN the East tomorrow morning. there
Will have occurred an event which is
regarded as one of the most important
OF astronomical phenomana. During
that time the planet Venus will have
crossed the disk of the sun, and obser-
vations will have been raede, for which
preparations have been going on for
months, and in many cases for wears.
From the barren wastes of Siberia the
plains of India, the deserts of Erypt.
from China, Japan, from islands 81 the
Pacific and Indian oceans and from
from the hills of Australia, this transit
Will be observed by the scientific men
sent out by the governments of Europe
ana the United States, and by the friends
OF science. Never before has the sun
and Venus been so observed as they
Will be tonight, according to our time,
between the hours of half-past eight
and one o'clock. They will be gazed
at with equatorial telescopes and with
refracting land rejecting telescopes
mounted on legs, and telescopes with
no legs at all. Their movements will
be timed by chronometers and chrono-
graphs, photographed with cameras,
aided by heliostats, and even their very
composition and the nature of their
atmospheres will be determined by
means OF the spectrosc ope. Is it to be
wondered at that Venus so seldom
brings herself into such a prominent
position, that her last appearance was
IN l769, and after again appearing in
1852, will not again be seen on the
suns disk until the year 20O4 This
transit furnishes the best means that
astronomers have of computing the
distance OF the sun from the earth. TO
lind the distance the moon is from the
earth, astronomers take the radius of
OF the earth as base line, and having
found the angle which Is subtended at
the moon by this radius, the distance
is easily calculated. This angle is called
the paraltar, and the suns distance
could be found the same way, but on
account of the great distance It Is from
the earth, this parallax or angle sub
tended at its surface by the earth's ra.
dlus, becomes unappreciable. By DR..
nalley's method the astronomer takes
the parallax of Venus at the point in
its revolution nearest the earth, called
its inferior conjunction. But as Venus
revolves between the sun and the earth
observations cannot be taken, because
the bright rays of the sun render it
invisible, except on those rare occa-
sions when it Is projected on the suns
disk. Its parallax being found, it is
comparatively easy to calculate the
parallax of the sun and its distance.
From observations taken during the
transits of 1851 and 1863 the distance
OF the sun was computed by Hencke
to be %, ,274, 600 miles, and the parallax
of the sun was calculated by Ncwcomb
TO be.8 ,S49 seconds and by Stone to be
8.9l seconds. 1t is certain that the
true parallax is within one tenth of q
second of these and it is desired to take
observations which will be correct to
the ono hundredth part of second,
which Is the anglo subtended by hu-
| man hair at the distance of 4, 800 feet.
To do this the most accurate instru-
ments will be needed and have been
procured, and all the improvements in
optics and its cognate sciences, which
have been made in the last century,
will help to make these observations
more correct and perfect than those
hitherto made. The same instruments
will also be used in 1882, when the
transit will be observed here, the most
available stations being on our Allan
tic coast. Our Government has five
parties stationed in the lower hcmis.
Iphere, as. follows: In Campbelltown
and Hobart Town, TASMANIA at Bluff
Harbor, New Zealand, at Kerguelens
Island and at Chatham.Island. In the
north there are three parties, at Via
disvostook and Nagasaki, Siberia, and
Pekin, China.
| ]. c. FARRA.
WILMINGTON, Dec. 8, 1874.