The Albany register. [volume] (Albany, Or.) 1868-18??, 1874-11-27

duu represent Gn0 0ar6Q, F0nuS anu
the sun at the time of transit. An
observer at would see the planet cross
the sun in the line d c, while an OBJ
server on the other side of the earth, at
B, would see it cross the sun in the line
G. These two lines are of unequal
length, and the transit, to the observ-
ers, would be accomplished in unequal
periods of time. By noting the exact
time and duration of the transit at these
two stations and afterward comparing
them, the difference between the paral-
lax of the sun and that of Venus can be
obtained, and from this the parallax of
the sun, and then the suns distance
from the earth. It is, of course, impos-
sible to obtain stations on directly op-
posite sides of the earth, to watch the
transit, yet places are selected as far
apart as possible, and the necessary al
lowance made in the calculations.
It may at first seem a very easy thing
to take these observations but in real
ity it is very difficult to make them ac-
curate. The instruments may not be
exact in every particular, and small
error, in measuring an angle at SO great
a distance as the sun, will make o great
difference in the result. Clocks may
differ by one or two seconds, and the
state of our atmosphere will affect the
distinctness with which the planet Is
seen. Then it is extremely difficult to
tell the second when the edges of Venus
and the sun meet, for, as they approach,
the dark edge of the planet appears
drawn out toward the sun before it really
touches it; and the difference between
the real and apparent contact may oc-
casion serious error. Hence the great
Importance that everything be prepared
with the utmost care, and that so far as
possible there be uniformity in the
methods of observing at the different
stations.
Another science aids the astronomer
in this work by giving him new meth
cd of measuring small angles in the
heavens. It is that of photographing
the object, and then making the desired
measurement on the plate by an instru-
ment called micrometer. The SUI
has been photographed for the purpose
of studying the solar spots, for many
years, and the process has been per-
fected and used with great success. It
is thought that by this method much
more precise measurement can be OBJ
tanned than by the simple eye-observa-
tions.
For the past two years preparations
nave been in progress for the coming
transit. Our own government has ap-
prOpr1ated Tor the purpose one hundred
| and fifty thousand dollars.
Eight stations are to be occupied
| three northern and five southern. The
| northern stations are near Pekin, Yed-
do, and place in the neighborhood of
the Caspian sea. The southern sta
| tions are upon the island of Mauritius
Kerguelan's Land; Hobart Town,
southern part of Australia some point
in New Zealand and Chatham Islands,
east of New Zealand.
These stations are occupied several
months before the transit, in order that
the instruments may be well mounted
and tested, and the latitude and longi-
tude of the places determined, and every
preparation thoroughly made.
Other nations, especially England
Russia and Germany, have made exten-
sive preparations for observing the
transit, choosing different stations fav-
orable to the purpose.
Another transit of Venus will take
place in 1882, which will be in some re-
spects more favorable than this. III
will be visible in the Atlantic States
and more generally in the inhabited
parts of the earth. The various instru
ments now used will be kept for thai
transit, and it will be observed with the
same interest and thoroughness as the
present one. After these the next vii
be in 2004 /; SO if my Atlantic reader
would see transit of Venus at all, the,
must travel to a point where it can b.
seen in 1874, or have their smoket
glasses ready for the one that will oc
cur December 6, 1882.-PaDaeEiG Z
Smiley, IN st. Nicholas for November