The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1856-1888, 1874-06-20
THE A n OF VENUS.

The general reader is probably well aware that
a transit Of the planet Venus across the suns
disc, will occur early in December Of the present
year, and that the United States and the chief
governments Of Europe intend to improve the
seldom afforded opportunity by making a grand
combined attack upon the problem Of the suns
distance-or, to speak more technically, it's
.. equatorial horizontal parallax,'' which is SIM
ply an astronomers expression for the greatest
angle which would be subtended by the earth's
equatorial radius 10 an observer at the distance
Of the suns centre, whatever that distance may
be taken to be. Taking into account all prob
able errors Of longitude, local time, Photographic
and contact observations, it is assumed, as a
result Of the costly expeditions that will be sent
out for this purpose, that the existing uncertainty
on this point will be reduced to one-third Of it's
present amount, or to o. sec. but it is far from
unlikely that the probable residual error will be
no more than one-half Of the latter quantity
that is to say, our distance from the sun will
probably have been ascertained within 5000
miles, or about I-l8OOth part of its whole
amount. OF the higher scientific advantages of
such a result, 1t is hardly necessary to speak.
But, for the information of those who would in
quire as to it's direct practical uses, it may be as
well to explain that an accurate knowledge of
the suns distance is essential for the perlecting
of the lunar and planetary tables, and therefore
Of the science of navigation, as well as for many
other matters of practical Importance, such as
finding the true Iongitudes of places on the
earth's surface, which depend on the accuracy of
the Lunar Theory.
Horrox, Of England, in 1888. was the first who
predicted, or rather calculated the transit of
Venus, in 1889, from which he deduced many
useful observations. Captain Cook made his
first voyage in the Endearor, TO Tahiti, to OBJ
serve IL transit of Venus in 1869. This expedi
ton was undertaken in consequence of a memo
rial presented to King George Ill. by the Royal
Society, setting forth the advantages which would
- 49, -- parrUI
of the then approaching transit wero takon in
the South Sea. Cook reached Tahiti in 1863.
BY a comparison of the observations made on this
transit (June Sd, 1867 from the various parts of
the globe, ON which it was viewed by men of
science, the distance Of the sun from the earth,
as calculated by this and later transits, is COM
puted at OF 0 5000 miles, instead of the COM
monty received computation of 95, 000, 000.
\ late number Of the London Mail april 6th)
has a very lengthy and highly interesting article,
descriptive of the energetic and complete arrange
ments which England and other countries are
now making for the observation, during the pres
ent year, of one Of the most rare and scientific
ally valuable of celestial phenomena. We make
room for several paragraphs, regretting that we
cannot reprint the article entire.
Guided by conditions such as we have indicated,
the Astronomer Royal has chosen five principal and
three subsidiary stations for our share in the enter
prise. Honolulu will be the chief station for obserY-
ing the accelerated ingress, and it will be strength
ened by secondary stations at two other points, prob
ably Hawaii and AtOOi, in the Sandwich Islands.
The retarded ingress will be observed at Rodriguez
Island near the Mauritius, and at Christmas harbor
in Kergueen Land (sOmetimes called the 8" Island
Of Desolation y, In the Southern Ocean; with a
station auxiliary to the latter at some second point
on the same island. Lastly, Christchurch (New
Zealaud) and Alexandria will pair together for the
accelerated and retarded egress, supported by indie
pendent observations which will be made in Austria
liza and Northern India. As Delislean stations, all Of
the above are excellent For IIalley's method, Ker-
guelen and its satellite, though not of frst-class
value, are good, probably the best practicable, south
ern stations; Christchurch and Rodriguez are of in
feriOr value IN this respect; and the rest are ex-
cluded, the whole Transit not being visible from
them. Parties, each consisting Of q chief astrono-
mer in charge, at least one solar photographer, and
from one 20 three or four assistant astronomers, will
be sent to the five principal stations. There will also
be attached to each party two or three sapper photo
graphers from the Royal Engineers, q number of
WhOm have Oeen uuuer instruction at Chatham by
Captain Abneys RE, IN the use of the photoheliO-
graph and the manipulation Of sun-pictures. Sir
George Airy's arrangements for the personal staff
are not yet complete, but, so far as is decided at
present, Captain Tupman, R.MA., o well-knoRn
member Of the Astronomical Society, will conduct 1
the Honolulu party, and will be accompanied by 4
Professor George Forbes, Of the Andersonian Uni
versity, Glasgow, and others. Lieutenant Neate,
is nominated as chief for ROdriguez; and the
Rev. =. J. Perry fills the corresponding Office for
Kerguelen. The stations subsidiary 10 Honolulu and
kerguelen will be served by ~detachments from the
main parties. Major Palmer, RE, will have charge
at Christchurch, and Captain Ord Browne Qate
at Alexandria; Lieutenant Darwin, RE, and
Abney, RE, respectively undertaking the
photographic work at these two places. At the out
set Of the enterprise, several ful-psy officers Of Ar
tilleTy and Engineers, nearly sufficient in number
for the entire staff, and all Of them more or less
by previous knowledge, volunteered to take
part in it, and We believe that Sir George Airy was
anxious 10 avail himself Of the services Of q class Of
whom experience had shown to be well
fitted for work Of the kind. But at this point the
Admiralty or the War Office, or both together, failed
him. With the three exceptions We have named,
the services Of these officers were refused, on the
score Of expense, and as an alternative a call was
made for volunteers from officers Of the Royal Navy.
Fortunately, men Of energy and ability responded
10 this appeal, and have since applied themselves TO
the work with 4 zeal and industry which give the
possible promise Of success.
Besides such smaller items of equipment as de-
telescopes, portable transit Instruments, tele-
graphic apparatus, cOmpasses, chronometers, baro-
meters, &c, four chief Instruments, each with its
portable observatory, solid stone platform, astrono-
meal clock, and other necessary gear, will be sent
o oil the principal stations. First in order come the
transit Instruments, Of forty inches focal length and
hree inches aperture, mounted on massive stone
iers. These viii be used FOR finding time by the
ransits Of stars, and longitude by tTansits Of the
noon. We have seen that II is an essential condition
f Delisle's method that the T~siGtire time at any
air Of stations shall be exactly known. Astrono-