The evening light. [volume] (San Antonio, Tex.) 1881-1883, 1882-09-23
TRANSIT OF VENUS.
Interesting Lecture by a Learned Belgian
Astronomers.


Astronomer.
[E%spo'r rte specially for the LIGHT by H. Ryder
A small but select audience attended the
Casino last night to hear Prof. Houzcau's lee
ture on the transit of Venus. Prior to the lee
turc Prof. Barbour Prof. w. B. Sterling ana
Mr.. John Harvey gave concerted perform
ance of the "Grand Republican March, Tor
which they received applause. This was fol-
lowed by "A very clever cornct sol" Inc sweet
est Flower Waltz" by Mr.. Harvey.
Alderman John I'll. Copeland, president OF the
San Antonio Literary and Debating Society,
introduced the learned professor as director
| of the Observatory Royal of Brussels, Member
of the Academy of Sciences and honorary
member of the San Antonio society.
Professor Houzea then came forward and
said 81 labor under the difficulty OF having
| to address you in a language not my own ana
hope to give you a few facts III relation to the
| transit Of Venus over the disc of the SUM- 1t Is
| a rare phenomena occurring at intervals OF
years, - years and l"J years. For instance
one transit occurred in l62S as noticed by the
as. rOnomers of that time Eight years after IN
| 1896 il w;ls again observed in England by two
astronomers. Again in l16l 1t was observed Dy
| astronomers who went abroad TO ASA; III was
observed again in America during II69 ana
| from that time until 1874 no transit was OF
! served o. expected. Great preparations were
| n,si.. to take the observation of 1874. The as
tronOmcrs then had greater advantages than
| in former time. They relied upon newly dis
|
| lronOmcrs, upon better and more powerful III
s the SS" taken whist Venus %as PAS pas;
ing over it, but they practically failed:
The next transit will occur in 2CO4 which neither
we nor our children will see. That is why so
much interest is attached to the approaching
| observation, and why such endetvOrs are being
| made 10 take the transit accurately.
''ro understand this phenomena properly.
must remind you of a few facts connected win
tle sofa. system. You know that eight planets
rtvolve round the sun. Mercury, Venus, the
cIrth, Mars, Jupiter, Saturn, Uranus ana Nep,
tune. Only two of these planets, Mercury and
thCs sc are the only two planets which pass be
fore the disc OF the sun, or make transit, as
it is called. The transit or Mercury occurs
every seven or eight years. but the transit OF
Venus occurs at greater intervalSa as have told
"Accorlling to a law known and established
in mechanics, the distance Of the planet Is
known by it's revolutions, and comparative
table Gun be made. BY this means we make
map of the sun and planetary system, showing
| their relative size, but This does not give the
actual size You may make IL plan of house
showing the room and lObDleS Dut unless you
have scale upon it you cannot tel the sizes Oh
the rooms. 1t is thus with the solar system
, II le map of the solar system is such a plan
without scale. We have an estimate but nc
s ale. The observation upon the transit snow,
ing the distances from the sun can give us thai
| :, lie and for this reason so much stress is laid
upon, SO much importance attached 10, taxing
the transit. .
\
1874, were well made but untricd instruments
, were used, and it failed. Photography upOi
which the astronomers relied SO much, failed
To ascertain the absolute distance on the eartl
based it was necessary to compare the posltlOl
of the planet in passing over the disc or th'
sun. r'e photographs showed hove s the t fo
. Venus, but it was found that the sun expanded
upon the Photographic plate extending more
ON The one side than the other, preventing al
Ii,,,pn tn nj
Venus revOvcS round the sun III eighty-clgh
day that has been known for agcs,ilnd
takes broader circle than the earth, ana ever.
two years comes between the ciirth ana SUI
I There might be Il transit every two years wci'
: it not for the circumstance that the ctrth
| plane is not in the same circle as the pain o
Venus. They are not in the same plane but III
| clincd so that, except at the period OF NlSlbl
transit, Venus passes before the sun just abov
or under the earth on account OF the lncllIl'
| ton. =, E..
Il am frequently asked, can the transit b
! seen with the naked eyer l answer, yes; !
you will get piece of window glass ana moi
it over Il lamp or candle until layer OF lalnl
block is formed, then You will have smoke
! glass through which you can see the sun dis
u tmctly. The sun will then appear to you Tx
a little round red disc, and. when Venus is !
transit, black point will be seen entering tn
limb of the sun in the lower left hand corne
trdvcrsing ,nc disc and making lis exit on TN
| other side. The time OcCup pied III the transit
| Venus will be about six hours and Il quartz
| With ii telescope the black point OF Venus
: seen rs IL rOuuu black SpO.. The transit as see
in San Antonio will commence about elgl
s. o'clock and continue until about quartz
W past two O'Clock in the afternoon.
S, "Enquiries have been made why San Antonl
~ should have been selected as point for ODse
" yaion We are not the only party who nav
selected this spot. parry from the Natlon
observatory, Washington, will arrive here
about two weeks and will make observations
This city. The transit is visible IRON Lith
Kennedy to Cape Horn, and astr0n'
u mers will be scattered all over Il
r' American continent. TIe British and FrCnt
have STA ions in (ne'r respective. colonies; Ot
els will go to Chill and other points moe sOut
It's necessary for the observation to be mac
- in two points and Lake Kennedy and Cal
Horn are decidedly the best point Tor OOserV
-. | tiOn: but Canada is Likely 10 present clOut
OF sky and there are similar difficulties to confer
with in the extreme south. so we Dad 10 pu
. ON to Texas whe!e We may hope 10 meet
clear sky on the day of the transit. The ira
sit here W I'll be changed in accordance with u
the position occupied by the observer, al
from this circumstance the transit III Chlll W
be much longer tnan in other ptfls OF Anierle
."rhc observation TO ascertain the ulstan
, from the sun is difficult as the transit Occ
UrS about six hours. II is uilhcult 70 say
what moment the planet enters the sun ul>
and observations rs to time have not Deen =!
tivCntIy exact. In the last transit tnc POSili'
of the planet wa photographed AT oiHere
csS times to ascertain the distance from tne cent
of The suns disc and the elects oil IL cnai!@e
place. A ! that was needed TO So!ve tne pro
| lem of t.Ie distance from the tarth 10 the So
but photography failed, because as nave
ready said the sun expanded on the pnOt"gi
mic plates to the one side or tine other ANA
was impossible to tind the exact centre Oh
distorted disc. so that the transit oil Stl