Helena weekly herald. [volume] (Helena, Mont.) 1867-1900, 1882-12-21
The Reason Why.

Many of our readers may desire little
information regarding the object of all the
commotion in the scientific world over the
transit of Venus and the following, clipped
from the Virginia City Enterprise, may serve
as enlightment:
The main object Of all these elaborate
preparations is to obtain such observations
as will enable the suns distance from the
earth to be expressed in miles AS long ago
as 171G it was suggested by HALEY that the
transit of Venus would serve to determine
the suns distance. and the method has been
tried three times-at the transits of 1761
1869 and 1874. The transit of 1851 was OBJ
served by 176 observers at III stations, and
that of 1869 was equally well observed.
From the date furnished by these two tram
sits Encke, in 1885, determined the suns dis
tance to be about 95,000,0OO miles. This
was acknowledged to be the best determina-
tion possible from the observations. But as
time wore on, and as astronomers tried some
of the other methods of obtaining the same
quantity, it was found to be too large dis
tance to be reconciled with these latter de-
examinations. The transit of Venus of 1874
was looked forward to as likely to settle all
these doubts, many of which were supposed
to have their origin in the defects of the
telescopes used by the observers of the
eighteenth century. The expeditions of 1874
were supplied with the best instruments
possible, and, besides this, they had the great
advantage of employing photography to reg
lister the positions of Venus on the suns
Disc The photographs were not affected by
any of the uncertainties to which even the
L - 1.o11
of the photographs could be made at home
at leisure, and could be repeated as many
times as might be desirable to insure ac-
curacy. 1t may be said that the results of
the eye observations Of 1874 Showed them to
be affected by errors of the same sort and
even of the same amount as those OF the
early transits.
The Photographic processes employed by
the European nations were certainly unsuc-
cessful. Fortunately, the American photo
graphs were taken by another method, and
the results from the discussion of these gave
a very satisfactory agreement. A conference
of European astronomers was held at Paris
in 1881 to decide on the methods which
should be employed to observe the next
transit. The results from the American
photographs were not known to them, and
they decided not to employ photographs at
the coming transit. The American Transit
of Venus Commission, however, do not share
these views, and they are to employ the same
Photographic methods in 1882 as were used
in 1874, and they confidently expect to obtain
equally good results.
The parties of the various nations are now
at their posts, which are scattered all along
the southern parts and the eastern and west
ern coasts of SOuth America all through the
West Indies, in New Zealand, Madagascar,
and the South of Africa. Every possible
precaution suggested by the experience of
the last transit has been taken, and if the
weather is generally good, it is not to be
doubted that the returns will be most credit
able to the science of our generation, and
that we shall not be ashamed to transmit
our observations to our successors. Nearly
the whole Of the United States is favorably
situated for observing this transit, and there
are enough astronomers, professional and
amateur, to insure a full observation, pro-
vided only that the winter sky is clear.