American citizen. [volume] (Canton, Miss.) 1864-1890, 1875-04-24
The American Observations OF the
Transit of Venus.

information from all the American par
ties for the observation of the transit OF
Venus At Pekin Prof Watson and
Prof. Young observed through a cloudy
sky the first and second contacts and
made forty four photographs during the
first part of the transit Operations
were then interrupted by clouds until
about an hour before the end, when the
Photographic work was resumed and
fifty more pictures taken. The third and
fourth contacts were also observed and
measures of cusps taken with the
double-image micrometer.
The first contact was sixty-eight sec
onds later and the second contact was
seventy-five seconds later than the COM
puted times, while the third and fourth
contacts were forty-three and sixty-five
seconds earlier than the predictions.
This indicates for the solar diameter a
smaller value than the one used in the
predictions, and agrees nearly with that
deduced by Leverrier from previous
transits.
1t was pointed out by Mr.. Hill, of the
American Nautical Almanac office, in his
memoir on the transit, that the English
predictions would be considerably in
error" on account of the adoption of an
apparent diameter for the sun which was
deduced from meridian observations
only, and we may note that nearly all
the English observers have reported an
error in the neighborhood of two min
utes in their predicted times of first con-
tact. 1t seems to be finally settled, if
indeed there was any doubt about it pre-
viously, that different apparent diane
tiers must be used for the sun in reducing
meridian observations, and for such OBJ
servations as eclipses and transits of the
inferior planets. This is quite analogous
to the fact that the moons diameter from
OSCILLATIONS is considerably smaller than
that derived from meridian observations.
Prof. Watson also notes certain evidences
of an atmosphere surrounding Venus,
and from his observations at third con-
tact obtains an approximate value for its
depth.
Land, under Lieut.-Coms. Ryan and
Train, has been only partially sue
cessful. Neither of the internal con-
facts was observed, but some photographs
were taken. The English party on the
same island observed the ingress and
egress, the latter observation being sat-
isfactory. All the English photograr his
were poor. The day was generally
cloudy, but enough have been secured to
compensate the observers for their devo-
ton as this station is peculiarly valua-
BILE. From the party at Chatham Island,
under Assistant Edwin Smith, of the
Coast Survey, we learn that nothing val
liable in the way of observations of the
transit could be obtained, on account of
clouds 1t must be remembered, how
ever, that each of the parties has made
important geographical, magnetic and
other determinations, and that no one OF
our expeditions will return without CON-
plotting its work of this kind, which work
has "A value quite Independent OF its
hna 10 m
parallax.
On the whole, the success has been
| marked; and although one party
| prof Watson's) observed all the con-
| facts, and although only one prof.
| Peters, obtained a very complete set OF
photographs, yet the ensemble of the OBJ.
servations of the Americans alone would
! suffice for an extremely accurate deter
mination of the parallax.
| The cxperience gained in these eXpe-
! ditions will be turned to good account In
1873 and in 1882, in which years transits
| of Mercury and Venus occur, both being
| visible in America. The reports OF all
| the parties indicate satisfaction with
the apparatus provided for them; and
in the matter of Photographic arrange
| ments the American outfits were partlcu
larry good, both theoretically and prac'
| tically, and this perfection reflects great
preparations in charge. The highest ties
timunial has been offered by the Transit
of Venus Commission to Dr. Henry
Draper as an acknowledgment of his
great land gratuitOus) services i'll per
fecting the practical details of the pho
tographic processes charge for which
he was peculiarly fitted by his long ex
perience in such researches.
Detailed accounts of the physlca
Of no
available for some time; but we note
the remarkable observation of JansseI
in Japan, and De la Grye at Campbell
Island, which declared Venus to have
been seen projected against the suns
corona while yet some distance from tn!
suns disk Preliminary reports indi
cate that Prof. Watson's account of thu
atmosphere of Venus will be corrol
Grated by several good observers. l
, may like wise be noted that the question
as 10 the existence of a satellite to Venu
l is now finally settled in the negative.
/ Editor's Scientific Record, IN Harper
7 | Maga7ine for Nay