, 1874-02-22

Great preparations have, for long time, been
making to observe the crossing Of the suns disc
by the planet Vanns. On the 9Th day Of December
next. Governments and scientific bodies mani
fest extraordinary interest in the matter. Con-
gress, some time ago, appropriated 4150, 900 10
aid in making the observations The French
National Assembly has voted 500, 600 francs for
the game purpose while Russia, England, and
tho German Empire have also devoted largo
Sums to assist in the enterprise. For ten years
the astronomers Of the world have been discuss
ing from what points the observations should be
made SO as to insure the best results
possible. Tho stations have been decided on.
the instruments are all ready for the expedition,
and the sardnts to take part in the undertaking
hare, We nre informed, completed their prepara-
tious, or are on the point Of completing them.
The passage Of the planet over the face Of the
sun will be visible only IN part Of Africa, in
Eastern Asia, in Australia, the Southern Seas,
in Greece, Turkey. in the Pacific Ocean, in Vic
toria, and the south OF Russia. The English are
going to make an effort to observe the transit
from Victoria. There are to be stations OF OBJ
eeryation at Bourbon, Tahiti, Pokin, and Yoko-
hama. The Russians alone expect to watch it
from twenty four different points.
The object Of Ill this preparation is to
ascertain whether the accepted value Of
the angle called the SUMS parallax is correct.
The true determination Of the angle in ques-
tion depends, OF course. on the accuracy Of the
measurements made OF it. And, since our
knowledge OF the earth's distance from the sun
rests upon the correctness Of our information
used in. calculating it,-it ia easy to see why SO
much interest is manifested in ascertaining
whether or not tho figure obtained by obsery-
ing the last transit does not need correction.
The last transit OF Venus was made in 17G9.
There will be another Dec. 6, 1882, after which
time there will not be- ono till June 8, 2oo4.
Till about ten years ago the astronomer Encko's
calculation Of the suns parallax.-a calculation
made in 1924, and based upon the observations
Of 1769,-was universally accepted Encke COM
puted tho SUMS paralla1 to DO 8.57 seconds.
which gaEe for the eartha distance from the sun
a little moro than $4,000, 900 miles. For rome
years, however, it has been surmised, TIC might
almost say demonstrated, that VIC are two to four
million miles nearor than this to the centre OF
our system. Leverrier, from various data, came
to tho couclusion that Enckn's figure WAS too
small by one-thutieth Of itself. Foucau1t, by
experiments Oh the velocity OF Light, showed that
the suns para1lax must be s.86 seconds. Han
zen arrived at like conclusion BY different road.
In 1862, ars VAS observed in oppos1tion With the
sun, from stations in Europe, the Cape OF Good
Hope, and Australia From the data obtained
by the observers at these points, Stone and Vim
necke reach the conclusion that the parallax Of
the sun muat be 80 seconds. 4 young astrono-
mer, Powalky, re-exsmined the figures obtained
in 1769, and found that they confirmed the con-
clusions reached by Lever1ier, Foncault, Han
sen. Stone. and Wlnnecke. Since this time the
paralla1 Of the Sun has bee><1As at between 8.84
seconds and 8.94 seconds. The 9Th Of December
next, clear weather favo1ing, will decide
whether this figure is the true one.
Before the pa1a1la1 Of the sun Tas measured it
Was not possible to discover how near our earth
Is to- it. Up TO the seventeenth century, people