The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1856-1888, 1869-08-14
THE PACIFIC
Commercial Advertiser.
AUGUST IA.
The Trnnsits ofVcnus.

Society of England about the beginning Of the
present year. This PAPER relates to the prePara-
tory arrangements necessary for the efficient OBJ
seryation of the Tran-its of the planet Venus
which are to occur in the years 1874 and 1882;
specifying the points on the earth's surface where
the most important observations are to be made,
and which Of these points should be especially
provided for by the British Government. As
Hawaii comes in for n share of attention in this
matter we find ourselves interested.
In order to the appreciation of the Importance
of these observations it may be well to point out
their object and nature The problem prepara-
tory to all celestial measurements is To ascertain
the size Of the earth itself. This, We need not
say, is done by actual measurement, in miles or
metres, Of a given arc or fraction Of the earthIs
circumference. The diameter Of the earth, thus
ascertained, il taken as a base line with which 10
trianguIate to the heavenly bodies and ascertain
their distance. In the case OF the moon this can
be done also, with some degree of accuracy, in
the case Of Venus and Mars when those two
planets are nearest the earth. But to triangu-
late directly, say to sumo particular spot on the
surface Of the sun, is found 10 be impossible;
while the distance to the sun is a very important
element. Without it, it is impossible to obtain
either the distance or size Of any heavenly body
except those aforementioned. Given this unit
Of measurement, and the Dimensions or the whole
visible universe are in the range Of mans knowl-
edge; estimate it wrongly, and the whole as
tronOmy Is n falsehOOd-
a very rare celestial phenomenon furnishes the
means Of knowing precisely how large the earth
appears when seen from the sun, and hence of
dcducing from the earth's diameter its distance
from the sun, ON the came principle that We may
knox precisely how distant a pole just six feet
high is from the eye, by measuring the angle it
subtends. This phenomenon is the Transit of
the planet Venus across the suns disk, which
happened last in 1863, and will occur again in
1874 and also in 1892. At such n transit the
planet is seen to enter on the eastern edge of the
suns disk and travel slowly across to the western
edge, occupying some hours in the passage. As
the planet is at only about one third of the dis
lance to the sun, any one can sec, by n little re-
Fiction, that different observers on different parts
of the earth will sec the planet on different parts
OF the SUMS disk. Almost every parlor has a
circular molding in the centre Of the ceiling. If
not, stick a round piece of paper there. Call
that the sun. Suspend from it by a thread a
mail black ball. Call that Venus. Set n ter
~rcstrial globe directly beneath on the floor, which
viii Of course D. earth. From the eastern
side Of the globe the black ball will appear much
further 10 the west than from the western side.
By simultaneous Observations ON opposite sides
of the earth this difference can be estimated,
which is the quantity wanted in the problem in
question.
In 1909 Capt. Cook was sent to Tahiti by the
British Government 10 take the first accurate OBJ
sc. .aiiOns OF this lind. while other observers
went n Lapland. Astronomers have for some
time suspected thu there were slight errors in
the observations that time, making the dis
lance some three u lions OF miles too great, and
VII be on the . TT in 1874, to correct them.
Perhaps We eau low why Honolulu is one of the
Two most available and important stations for the
observations Of that year. Venus enters the
suns disk at ii hours past noon of Greenwich
time on Dec. 8. 1t is then noon ut Queensland,
Australia. The declaration of the sun is go
south. That is the latitude Of n point on the
coast Of Queensland, and there the sun will be
vertical on that day. Now elevate the south
pole of the globe % : and bring Queensland to
the brass meridian. The disk in the ceiling of
the room will then truly represent the position of
the sun at that time. All that part of the globe
beneath the wooden horizon will not see the phe-
nomenon at all. Honolulu is two hours above the
wooden horizon. The sun will therefore be two
hours high at this place. Venus enters on the
Y. e. side Of the suns disk, and Honolulu, in
that position of the globe above specified, is on
he N. E.. side, and is the point on the earth
where the transit will commence the soonest and
where the most difference of position to the west
rard will no nIzarved Tf srauda fber. Fora No I |
the list of places for observation, and Prof.
Airy has given it that place only, buried in the
iepths of the Greenwich Observatory, he persists
n the name "a Woahoo,' - and does not know that
line Of steamers connects this port with the
ivilized world. The opposite place for observa-
ion is Kerguelen's Land. Mauritius is more
asly accessible and, being for practical purposes
learly as good as the aforementioned point, will
be chosen
Now to make this point, (Honolulu) properly
valuable, the precise longitude of n well-6tted
observatory on shore should be ascertained. If
he British or American Governments, or both,
would assist in the establishment Of n good per-
nament observatory here it would be a benefit,
lot only in the matter in question, bot to the
ause Of science in general. Punahou would be
N excellent locality, and for various reasons.
In observatory is always best out Of town, be-
ause facilities for adjusting meridians are more
{ command there is less dust there is less jar
ing from passing vehicles; and less interruption
visitors The neigbborhood of an ~institu-
ion Of learning would be a mutual advantage.
An observatory should possess an equatorial
elescopc worth say $4,000, an astronomical clock
which with It's fixtures should cost about $500,
nd N fruuGft fnafruncnf IF ssr faof fopo
on granite blocks, and to cost about
1000. $500 more for a building would make
he sum of $4,000; not an appreciable expense
Or q powerful government. All these above
instruments would Of course be of no
vail without a competent observer. Five years
5 none too long a period to allow for adjusting
verything necessary, and for the important mat
er Of precise determination Of longitude. If,