The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1875-03-22


OF one revolution OF the mlcrometrlc screw and
also tested carefully ITS regularity. Tue error OF
level OF the Photographic telescope was always
very carefully determined. as you viii when
the RECORDS reach you. The measurement OF this
error | made with the micrometcr, using tae
spirit level OF the engineers level only Tor small
amount-usually not half a division of its scale.
THE METHOD ADOPTED
you will understand clearly from the records. The
aZimutn oil the middle vertical line OF the plate
holder and also the azimuth of the plumb line
wnere 1t crosses the middle horizontal line
of the plateholder, were carefully measured
each night OF observation. In the case
OF the double image mcrometer took
large number OF transits OF the sun
limb to determine its zero point ana the value or
one revolution OF the screw. me nlent before
(Lhe transitl had been beautifully clear. went
IA person 20 the opservatoIS az ~ IL, n -.
M. and observed Tor some time. also MADE
mai inspection TO see that everything was all
right. assigned 10 each member the duties he
was 10 perform, ana every man was III DIS place
long before the appointed time.
We had measured the distance between the
objective and plateholder, and we were proceed
Ing To make reversed photographs OF the lines
wEen a Dank oil CLOUDS came up rom the south
east and covered tue sum- 1t began To appear
hopeless Tor the observation OF the transit.
/ mad arranged so as 10 have the contacts OBJ
served Win three teIescopes-vlz., Dy myself with
the nve.incn equatorlal by Professor Young with
the tnree-Inch clark telescope, and 10y Mr.. Wood
wa.d with Professor foungs four-lncn comet
seeker, he rising clouds preventing Professor
Young from using the speclroscope. Inc clouds
were getting llttle thinner aud the prospect
was, a 1.-THE before nine O'Clock, favorable lor the
observation Of the FIRST contact.
JUST As WE WERE READY
to compare cAronometers IL WAS discovered that
tne electric connections between the Photographic
house aud the transit house was broken, and fro-
ma d0f the place OF the break. But as It
lacked only half hour OF the first con-
e na TO be to sure and have eG inc ns
exposure OF the phoi oeraphs taken SHARPLY
l sent MIR. Woodward INFO the Pho tographc house
10 maze the record and take tne lime Dr.
Dudgeon, the surgeon OF the BRUSH legation had
kindly under aSen 10 do this service Tor Us; but
the accident to our electrical connections made IL
necessary Tor Inc 10 assign Mr.. ood"ard 10 this
duty. He dId not therefore observe the first and
second contacts. The first and second contacts
were observed py me and Professor Young
TIN ougn tnln clouds, ana the photographs bear
evidence of the difficulties we had 10 encounter
The neliostat was IN charge OF Professor Young,
and wnile ne was engaged ln.obsefVing the con-
facts Win telescope near by. lie was assisted by
the Rev. Mr.. Collins III lts management. IL was
next To Impossible 10 try TO eaten the sun in pass
ing breaks In the clouds, and hence gave the or
der TO 90 right ahead and photograph as rapidly as
the states were ready ana KNOW tnat oy SO cong
we got many more pictures which can I've mea-
sured tnan would oiherwlsc have been possible.
Sometimes the bright spot IN the CLOUDS hot eX-
actiy over the suns centre would mlsead the man
at the helostat ana ne would dlrect the image Of
the spot, instead OF the sun, TO The centre Oh the
diaphragm. There are three or Iour photographs
winch IN This way are on tue SIDE ol the plate We
had provided rings, visible from the outside, so
that wnen ouds did not interfere we could direct
the image Almost exactly TO- the middle OF the
plate noIuer. on the whole, you Will 1nd the Pic
lures wen centred on the plate the exceptional
cases beng those mentioned.
After iorty-1our exposures had been thus made
dense clouds Obliged us to suspend operations.
1t remained completely overcast until near one
O'CLOCK p. NJ, when we were enabled TO resume
Photographic
Meanwhile we mad detected the place OF the
break In our wires now supposed 10 have been
made by Chinaman with a wheeDarrow loao OF
water passing over the wires Just before we alseov
ternoon photographs are also recorded on IN .
chronograph. 1 also continued Mr.. Woodward at
the record OF the tunes, &C., and DR.. Dudgeon gave
valuable assistance III developing ana fixing
the photographs, winch we MADE at average IN
tervais OF minute ana 9uarler. u WI ne
with the corresponding record by the CLOCK or the
cn1onograpn that the times are taken Dy nini Vita
entire accuracy, so that tGe forenoon times OF the
photographs as reliable as II tuey had
been also recorded on the cnronograph. we oe-
gan Lhoiographing in the afternoon as soon as
the clouds became min enough 10 enable US 10
see the sun, and gave the same order as IN the
Iorenoon-to make exposures as fast as the plates
coula be got ready. BY 50 doing We obtained
Ity-lve exposures before the end OF the transit.
The clouds spersed before the third contact, but
dust storm was approaching tt actually came
hour alter the translt, and the air was yellow.
tinted with gust, SO That long exposures mad to
be mace.
APPEARANCE OF THE PICTURES.
The photographs are necessarily thln. but nearly
all OF them eau be well measured. lie third anu
fourth contacts were observed by me with the
eQuatoriAls by Professor Young with the three
inch Clark telescope and by MI. OOuWafu WITH
the lour-inch comet seeker. In measuring cDsps
/ was bothered IN the forenoon by ne tantness
ON account or clouds and In the afternoon Dy tue
unsteadIness OF tue linD at times However,
did the best could, ana succeeded In getting be-
tween thirty and forty measures.
70 recapItulate them We nave observed well all
the contacts, and nave obtained about ninety
photographs which can De measured | regret
mat we ana not have a clear Gay, III which case
We should nave Obtaincd 200 Qood photographs.
The observations Tor position OF the Photographic
telescope and ali necessary preliminary oDserva
81 rel
we nave the means OF getting from our pnoto-
graphs all tnat Is OpticaIly possible, ana nope
mat no pains Will lie spared in their measurement
In accordance with your suggestion nave d.
/ vlded the negatives. l have retained here, to be
forwarded On INHERENT steamer, one box Of
negatives, containing three sets uour each) OF
direct and reversible photographs, one before and
two after the day Oh the transit and tniry-egnr
negatives Of the transit Those which nave are
good negatives, and ii the Others should unioflu-
result lor Pekin. those wnlcn | have retained
win carry TO hong Kong and pat IN the personal
charge o. the COMMANDER OF tue PACING Mall
steamship sailing directly 10 San FRANCISCO, to be
thence forwarded WITH great care by express to
washington. / Will also forward, through tne
Department OF STATE the original records and the
dupca tie, directed III the printed INSTRUCTIONS.
Inc instruments particularly mentioned IN your
letter oil the 22d October and The negatives, except
those | shall send from Hong Kong, have gone
forward III charge OF Professor Young. lie Will
deliver them 10 you IN Washington.
Tne otner instruments are - go nome IN the
l Lackdwanna, when Is soon to return 10 the
United states. enclose herewith
we observed them, and 1 desire at the same
time 10 call yonr atteDt iOD to the phenomena oil
I these contacts 1 observed them, which are
quite different rom those the artificial transit
which observed. The ialntness OF the Image
at the second contact, caused ~ tue thin CLOUDS,
dld not enable me TO see the changes definitely
III the afternoon at third contact, but Cld see
well enough TO put me on the Lookout Tor dennl te
phases at third contact and to snow me what TO
I expect.
fnGs while the third contact was observed BY
me Win great accuracy and under favorable cir
cumstances, | am satisfied that my oOserv2 tons
OF second contact are very good ana To be relied
/ upon IN the discussion OF all the observatloas
The records Will gly9 you an account OF what was
seen by eacn observer and now write simply 10
state what now KNOW 10 De the phenomena VI
actual transit. Will describe
/ THE THIRD CONTACT,
! where | every phase clearly and unmissas
ABLY. Frat. wnen the Uand OF lI2nt between
! Venus and tne suns lImD was reuuced TO about
one second OF arc Tor perhaps O.ss.) IN width
It was Interrupted by nlulng shadows. They be
gan ny single one mOmentarlly III the tnlnnes
part OF the Uand, then expanding as the Dend be-
came thinner and tninner-not pei manent, Du,