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^Accessions No. <F3<?£~
OBSERVATIONS
OF THE
TRANSIT OF VENUS,
9 DECEMBER, 1874;
MADE AT STATIONS IN NEW SOUTH WALES.
ILLUSTRATED WITH PHOTOGRAPHS AND DRAWINGS.
UNDER THE DIRECTION OF
H. C. RUSSELL, B.A., C.M.G., F.R.S., F.R.A.S., &c.,
Published by Authority of Her Majesty's Government in New South Wales.
CHARLES POTTER, GOVERNMENT PRINTER, PHILLIP-STREET.
5d 35—92 a 1892.
INDEX.
PAGE.
Mr. Russell's report ... ... ... ... ... ... ... ... ... ... 1
Mr. Leneban's report ... ... ... ... ... ... ... ... ... ... 8
Mr. Savage's report ... ... ... ... ... .. ... ... ... ... 10
Mr. P. F. Adams' report 11
Mr. Vessel's report ... ... ... ... ... ... ... ... ... ... 15
Mr. Hirst's report ... ... ... .'.. ... ... ... ... ... ... 19
Mr. Du Faur's report ... ... ... • ... ... ... ... ... ... ... 20
Mr. Fairfax's report ... ... ... ... ... ... ... ... ... ... 23
Captain Hixson's report... ... ... ... ... ... ... ... ... ... 24
Captain Onslow's report... ... ... ... ... ... ... ... ... ... 27
Professor Livcrsidge's report ... ... ... ... ... ... ... ... ... 28
Mr. Tornaglii's report ... ... ... ... ... ... ... ... ... ... 29
Kev. A. Scott's report 80
Mr. MacDonnell's report ... ... ... ... ... ... ... ... ... 34
Mr. Watkins' report 3U
Dr. Wright's report 37
Mr. Allerding's report ... ... ... ... ... ... ... ... ... ... 39
Mr. Bolding's report 39
Messrs. Belfield and Park's report ... ... ... ... ... ... ... ... 41
Mr. Belfield's report '. 42
TRANSIT OF VENUS, 1874.
LIST OF PLATES.
Nos. I to VII. — Mr. Vessey's observations, showing " Halo on disc," " Dusky ligament,"
" Eing of light," " Irregular shape of Planet," &c., &c.
Nos. VIII, IX, X. — Mr. Belfield's observations, showing " Illumination and colour of Planet
at ingress and egress."
No. XI. — Mr. Savage's observations, showing " Plash of light on outer edge of Planet at
egress.
No. XII. — Mr. Watkin's observations, showing " Elongation of Planet."
No. XIII. — Mr. Allerdiug's observations, showing the " Black drop."
Nos. XIV, XV. — Mr. Hirst's observations, showing the " Black drop " and " Fringe of
red light."
No. XVI. — Captain Onslow's observations, showing " Halo on sun."
No. XVII. — Mr. Lenehan's observations, showing " Halo and polar spot."
No. XVIII. — Mr. MacDonnell's observations, showing " Halo around Planet."
Nos. XIX, XX, XXI.— Mr. Park's observations, showing " Positions of illuminated edges,"
" Blue colour of Planet," and " Illumination of preceding limb."
No. XXII. — Professor Liversidge's observations, showing " Illumination on Planet " and
" Processes at egress."
No. XXIII. — Dr. Wright's observations, showing " Halo and polar spot at egress."
Nos. XXIV, XXV, XXVI, XXVII.— Mr. Eussell's observations, showing "Vibration,"
" Halo," " Polar spot," " Haziness," &c., &c.
No. XXVIII. — Mr. Bolding's observations of " Ingress and egress."
No. XXIX. — Mr. Fairfax's observations, showing "Eing of Light."
No. XXX. — Mr. Eussell's observations, showing " Eing of Light."
No. XXXI. — Sydney Observatory.
No. XXXII.— The lli-inch equatorial at Sydney.
No. XXXIII.— The photo.-heliograph.
No. XXXIV.— Transit of Venus, Camp, Woodford, New South Wales.
No. XXXV. — Waiting for the transit at Woodford.
No. XXXVI.— Waiting for the transit at Eden.
No. XXXVII. — The 7i-iuch equatorial used. at Eden.
No. XXXVIII.— The 6-inch equatorial used at Q-oulburn.
No. XXXIX.— Photo taken at Sydney. Time 3h. 13m. 13'52s. S.M.T. (Eeproduced directly
from the negative.)
Inch squares placed at a distance of 400 feet and photographed with the Sydney equatorial as
a test of distortion. (See page 2, Sydney observations.)
No. XL.— Photo, taken at Eden. Time, Ih. 9m. 55'89s., S.M.T. Photo, taken at Woodford.
Time, Ih. 55m. 5Gs. S.M.T. (Both reproduced directly from the negatives.)
INTRODUCTION.
IMMEDIATELY after the very satisfactory observations of the transit of
Venus, made by the observers in New South Wales, it was decided to
ERRATA.
Plato I, Fig, 3, the time should be 12 hours 15 minutes 30 seconds.
Plates VII and IX and X. Read Armidale, New South Wales.
Plate XII. Bead Eden, New South Wales.
Plates XIV and XV. Read Mr. Hirst's observations at Woodford.
Plate XVII. Venus should be numbered 1, 2, 3, 4, beginning on the right.
Plate XVIII, should have Eden, New South Wales on it.
Plates XIX, XX and XXI. Read Armidale, New South Wales.
Plate XXII. Read Ooulburn, New South Wales.
Plates XXIII, XXIV. Read Sydney, New South Wales.
Plate XXVUI, on diagrams 4 and 5, read " egress " for " ingress," " Holding" for " Balding.'
Plate XXIX, for Sydney, New South Wales, read Woodford, New South Wales.
Plate XXX. Read ring of light at ingress, an enlarged view of 6g. 3, plate XXVII.
Corrections to Mr. I'e&sey's Report.
h. m. 8. h. in. s.
Page 16. For 12 7 OO'OO read 12 7 4(r60.
^age 17. „ 3 46 O'OO „ 3 48 O'OO.
Piim! 1H. „ 12 23 51 00 „ 4 23 52'00.
Astronomer for New South Wales, died, having taken no steps to prepare
for the transit of Venus observations. He had, indeed, expressed his
intention of taking no part in the work, owing to other pressing duties.
My appointment followed immediately after his death, and I at once took
steps ta prepare for the great astronomical event, fully realising the great
importance of taking advantage of our favourable geographical position on
the eastern coast of Australia for observing the egress. It was obviously
for the honor of the Colony, as well as for the advancement of science, that
the observations and photographs of the transit of Venus should be as
complete as possible. I therefore at once brought the matter under the
notice of the Government, asking authority to carry out the work, and a
vote to cover the expenses. My request was warmly supported by our
INTRODUCTION.
IMMEDIATELY after the very satisfactory observations of the transit of
Venus, made by the observers in New South Wales, it was decided to
publish in full the result of their labours with coloured plates and every
detail carefully revised by each observer, so that the printed diagrams
should represent in each case exactly what he meant by his drawings ; but'
the observers lived in widely separated districts, and so much time was lost
in revising the proofs that a considerable period elapsed before they were
ready. Meantime the Royal Astronomical Society deemed the reports and
drawings of sufficient importance to publish them, and had published and
circulated them before this volume was ready, and although some addi-
tional matter and diagrams will be found herein, it was at the time deemed
better not to publish at once. Various circumstances, however, combined
to delay the publication much longer than was at first intended ; but it is
hoped that the work will still be valuable as a record of the New South
Wales observations for the present and probably the next generation of
transit of Venus observers.
A short account of the circumstances which led up to the observa-
tions of the transit of Venus in New South Wales, will furnish explanation
of various matters which need such reference, notably the delay in com-
mencing the preparatory work, the instruments, and other apparatus used.
In August, 1870, Mr. G. R. Smalley, who had been the Government
Astronomer for New South Wales, died, having taken no steps to prepare
for the transit of Venus observations. He had, indeed, expressed his
intention of taking no part in the work, owing to other pressing duties.
My appointment followed immediately after his death, and I at once took
steps ta prepare for the great astronomical event, fully realising the great
importance of taking advantage of our favourable geographical position on
the eastern coast of Australia for observing the egress. It was obviously
for the honor of the Colony, as well as for the advancement of science, that
the observations and photographs of the transit of Venus should be as
complete as possible. I therefore at once brought the matter under the
notice of the Government, asking authority to carry out the Avork, and a
vote to cover the expenses. My request was warmly supported by our
vi INTRODUCTION.
Royal Society, who appointed a deputation to wait on the Government to
urge the importance of this work. Eventually, the Government gave
authority, and a vote of £1,000 to enable me to carry out the work.
This was in 1872, and inquiry elicited the fact that instrument-makers
in Europe had their shops full of work for European observers, and
could not undertake my orders at such a late period. Eventually, I
succeeded in getting one photo-heliograph with Janssen apparatus, and also
the object glass and micrometer for the large equatorial. For other apparatus
required, I had to look to mechanics in the Colony, for the most part
unused to such delicate work. This meant a great deal of additional work in
designing, overlooking, and generally seeing after what was done. To
provide for the photographic work, three cquatorials were fitted up with
photographic apparatus with which to take pictures of the sun ; others were
mounted on rigid stands ; chronographs, buildings, &c., had to be made
necessary to equip four observing-parties, each having transit instrument
equatorials, an independent observatory and apparatus for observing and
photographing the transit. By unremitting exertions everything was ready
by the middle of 1874, and the work of organising and training the observers
began, each party working in its own observatory, and with the apparatus
they were going to use at the several observing stations, but which, for
convenience, had been set up in the observatory groiinds. Everything
being quite ready the observing parties started in good time for their
several localities. The reports which follow record their success. It
would have been quite impossible to accomplish this had I not received
from all who could assist most enthusiastic support.
The following resume of the results was written immediately after
the work, while the written and verbal reports of all the observers were
fresh in my mind. It will serve as an introduction to what follows, and to
call attention to some points of importance bearing upon the physical aspect
of the ingress and egress of the planet, which may be useful to future
observers, and, perhaps, in rediscussion of the transit of Venus, values
of the parallax. But since these following observations were incorporated
in the final results obtained by British observers, and fully discussed by
the Astronomer Royal of England, Sir G. B. Airy, and also under his
direction by Captain Tupman, I do not propose to enter into that question
here, further than the quotation of a few sentences from the report upon
the general result of all the British observation, which was prepared by
Captain Tupman.
INTRODUCTION. vii
There were thirty-one British observers of ingress, whose reports
were available. Of these eight were from New South Wales ; but after
weighting and discussion, the total number was reduced to twenty. Of
these eight received double weight ; and of these double- weighted eight,
two, Messrs. Scott and Russell, are New South Wales observers.
At egress there were forty-eight observers, and again New South
Wales furnished eight. After weighting and discussion, forty-eight are
reduced to forty-one, but all the New South Wales eight remain, Vessey
and Russell getting double weight, and Allerding, Captain Hixson, Lenehan,
Liversidge, Dr. Wright, and Tornaghi, single weight. Captain Tupman,
on page 453 of the monthly notices, R.A.S., June, 1878, says : — " It is seen
that the observations at Sydney, New South Wales, viz., by Russell,
Lenehan, Wright, and Allerding, have great weight in lowering the value
of the parallax, and this effect is exaggerated by allowing Russell double
weight. Mr. Russell's is one of the most detailed observations made ;
- ~
it seems impossible, from his description, to choose his earlier time. Mr.
Lenehan admits he was late, and I have taken 10. seconds from his time, but
still it is late. Dr. Wright made ' the most accurate observation possible',
and agrees to a fraction of a second with Mr. Russell. Mr. Allerding does
not profess to have made a good observation. Out of mere curiosity I have
solved the thirty-five equations that remain, when Wilson's, Strahan's, and
those at Sydney are excluded, and find the mean solar parallax as 8"' 894"
In the previous discussion he made the parallax at ingress, in which the
New South Wales observations were retained, S"'845, and at egress 8//-846,
the mean of which, 8'8455, he accepted as the value of parallax from 1874
transit of Venus observations. Subsequent discussions show that this was a
wise course, for the most elaborate discussion of the solar parallax Avhich has
yet been made, viz., that by Professor Harkness, combining the results
from all available methods and published this year, 1892, makes the
mean of all the values obtained since 1769 to be 8'834, which shows
clearly that Captain Tupman was right in retaining the New South Wales
observations, although at the time they seemed to make the parallax smaller
than it was thought to be. This is strong confirmation of what appears in
subsequent pages, viz., the accuracy of the observations, made so by the
very favourable state of the atmosphere, and good telescopes.
As already stated, it is not proposed to go into a discussion of the
results here. I have merely quoted Captain Tupman to show what he
viii INTEODUCTION.
thought of New South Wales observations, and their effect upon the value of
the solar parallax, derived from 1874transit Venus, which was, as we haveseen,
to make it much smaller than was at that time supposed to be its value,
and to bring it more into accordance with all that astronomers have learned
about it up to the present year, 1892. It will be seen in the following
reports (page 5 and others) that the effect of bad definition is to make the
observer think contact has been made before it really is made, and therefore
v 3
a steady atmosphere is a most important factor in the value of such
observations, any unsteadiness of atmosphere tending to make contact appear
too soon, and therefore to make the solar parallax too large ; turning now to
the resume prepared at the time.
Never perhaps, in the world's history, did morning dawn on so many
waiting astronomers us it did on the 9th of December, 1874. They were
all anxiously looking for an answer to the old question, to be, or not to be,
and certainly none could have expected a finer day than that which
dawned on the observers of New South Wales. Prom all stations, in return
for the morning clock signals, came the welcome intelligence that the
morning gave promise of a splendid day, and after hearty good wishes had
been given and received, we all turned to the final touches, which were
necessary to complete our arrangements, and when these were done,
waited, not without an involuntary feeling, which I will not call excite-
ment, for that by common consent had been banished, but rather an
overpowering sense of that responsibility which every true worshipper of
science must feel, when he knows that the answer to half a century's
questionings is depending upon him ; and that he is the observed of all
observers ; but each one was determined to do his best in the noble cause
of science; supported by a faint hope that his name and his work would
appear ages hence in the records of science, and be criticised under that
blaze of knowledge which the united efforts of the world's science should
produce.
And here it may not be out of place to introduce a few words about
the selection of the New South Wales stations. Eor ingress there was little
choice, for, the sun being in the zenith of a place near the longitude of
Sydney, and in 23° south latitude, the parallax was almost nothing
everywhere. At egress, however, our circumstances were much improved
in this respect, and the south-eastern point of New South Wales was one
INTEODFCTION. k
of the best points of observation in Australia. In addition to this, there
were two conditions to be borne in mind in making the selection — viz.,
weather, and telegraphic convenience for determining longitude.
I had for two years previously caused special meteorological observa-
tions to be taken at various places during the month of December. These
indicated Woodford as about the most promising station for clear and
steady atmosphere, and made it evident that the observers should not all be
stationed at Eden, but be divided between the coast and the mountains.
Bathurst and Goulburn were alike in chance of clear weather ; but Goul-
burn was the better station geographically, and was therefore selected.
Eden weather reports were not encouraging ; but as the advantage of the
position was so much in its favour, it was decided to make it the fourth
station, and the Rev. W. Scott, formerly astronomer for New South Wales,
proceeded there with Messrs. W. J. MacDonnell and J. S. Watkins,
observers ; and Mr. Sharkey, photographer to the Government Printing
Office, as photographer, and one carpenter, with observatory, tents, instru-
ments, and all needful appliances. The telescope used by Mr. Scott was
a 7j-inch equatorial of 10 feet 4 inches focus (see plates XXXVI and
XXXVII) ; by Mr. MacDonnell, 44-inch Cooke equatorial ; and Mr.
Watkins, a 3^-inch equatorial ; they had also means of taking 220 photo-
graphs.
Captain Hixson, President of the Marine Board, Captain Onslow,
M.P., and Professor Liversidge, with Mr. Tornaghi, photographer, and a
carpenter, made the observing party at Goulburn ; they took with them
the 6-inch equatorial with the camera as shown in plate XXXVIII, the
observatory tents ; instruments, &c., which were similar to those at Eden,
but the telescopes were smaller, having 6 inches, 3f , and 3^ inches object
glasses. They had also means of taking 220 photographs.
P. F. Adams, Esq., Survey or- General, with Messrs. Hirst, a well-
known amateur astronomer, Mr. Vessy, of the Trigonometrical Survey,
Mr. Du Faur of the Survey Department, Mr. Bischoff, photographer,
and two carpenters, proceeded to "Woodford" the mountain residence
of A. Fairfax, Esq. Their instruments were the photo-heliograph and
Janssen apparatus, a 4| inch equatorial and one of 3^ inches, chrono-
meters, clock-chronographs and all necessary apparatus for 220 photo-
graphs, and 30 Janssen plates, each to hold 60 pictures. The observatory
6
INTRODUCTION.
was similar to that used at Goulburn. (See plates XXXIII, XXXIV,
and XXXV.) Mr. Adams gave me every assistance, and provided
Transit Instrument and another observing telescope, and two ordinary
tents.
At Sydney the observations depended wholly on the observatory
staff. The instruments were the 11^ equatorial (see plate XXXII), a 4f
Equatorial by Troughton and Simms, and a 10-inch Browning- With silvered
glass reflector, kindly lent for the occasion by J. Usher Collycr, Esq., with
all usual clocks, chronometers, chronographs, &c., and means of taking 220
photographs.
I cannot leave this part of my subject without expressing my Avarm
thanks to all who assisted me in observing the transit of Venus. With a
zeal worthy of the occasion, one and all devoted themselves to a course of
previous practice at the Observatory which involved an amount of hard
work and self-denial worthy of all praise. This in some cases extended
over several months in order to make themselves thoroughly conversant
with their work ; and this not only during daylight working at the artificial
transit and photography, but also at night adjusting the instruments. My
thanks, however warmly given, can be no measure of their work. I shall
always feel grateful to them for their support, and for the enthusiasm and
the zeal with which they devoted themselves to the work, and for their
generous and thoughtful kindness and assistance to me personally in a
thousand ways. From the officers of the Telegraph and Railway Depart-
ments also we received the most cordial assistance ; indeed everyone for
once made common cause with the Astronomers.
Previous to starting, all the observatories and instruments were set
up in Sydney, and each party went to work in their own observatory ; this
we found to be of great service in pointing out weak points, which required
either more practice, or the instrument maker to set right.
For practice in observing, we had two artificial transits, one similar
to that designed by the Astronomer Royal, the other constructed in the
Colony. The one made in Sydney consisted of first a sheet of metal, out of
which a hole was cut 5 inches wide and 18 inches long, bounded on three
sides by straight lines, and on the fourth by a curve of such radius that at
a distance of 400 feet from where the telescopes were placed, it appeared
like a section of the sun's limb. Behind this opening a piece of ground
INTRODUCTION.
glass, worked in a slide, and on it was fixed a blackened disc of metal having
the apparent diameter of Venus. This was drawn along hy clock-work, so
that the artificial Venus appeared to come on to the sun's limh at external
contact, and gradually travel in and make internal contact, at which point
a most satisfactory black drop was seen. A large mirror behind all to
reflect a bright part of the sky completed the apparatus. Five telescopes
were directed to this, and as many observers, each using his chronometer,
observed ingress and black drop, and then compared their observations.
With this a great deal of practice was obtained, which was useful in
training for observation. At the same time all were warned that there
was no certainty about the black drop phenomena.
"We come now to the day's work, and take first the weather at each
station.
At Eden, the morning was fine and very promising, but about
11 a.m. clouds began to come, with a fresh sea-breeze, and led the
observers to anticipate a disappointment. Fortunately up to the time of
ingress the clouds had not interfered with the observations ; but from that
time forward the sun was more or less obscured, and at one period wholly
so for 80 minutes, so that few photographs could be obtained, and the sun
was entirely obscured some time before egress.
At Goulburn, the morning was fine, with light westerly wind and a
few drifting clouds ; during the afternoon the wind increased to half a gale,
and the clouds were more numerous, but not sufficient to interfere with
observation.
At Woodford, the morning was fine, with a dry hot wind (westerly),
which increased as the day wore on ; during the afternoon a few clouds
passed over and interrupted the photographic work for a short time, but at
ingress and egress the weather was splendid for observation.
At Sydney, the early morning was beautifully clear until 5h. 30m.
a.m., when a heavy bank of fog came in from the sea and obscured the sun.
for three hours; but we still expected a fine day, and were not disappointed,
for by 9 a.m. we had a clear bright sky and light north-easterly wind,
which increased to a fresh breeze during the afternoon. The state of the
atmosphere also was favourable for observation until the transit was over,
except a few moments of bad definition ; but had we been one hour later,
xii INTRODUCTION.
I do not think observations of egress would have been worth anything, for
clouds were rapidly forming in the S.W., and, though thin, they spread
very quickly over the sky.
Ingress.
For the purpose of convenient comparison I have arranged the times
of observation in a tabular form, and put all into Sydney time. I confess
when I saw the gradual phenomena of the transit myself I did not expect
such a satisfactory agreement between the times of observation as some of
the results show ; and if 4J seconds be taken as a fair estimate of the
probable uncertainty of observed time at one station, when a definite
phenomenon like the breaking of the black drop had to be observed, I think
we, with no such definite phenomenon to observe, may congratulate our-
selves that the differences are in most cases so small.
Only three out of thirteen observers took the time of first external
contact, and they were evidently a few seconds, probably about ten, late.
Such at least was my own impression at the time, for Venus had made
something more than contact, — it was a small notch in the sun's limb.
My time is llh. 56m. 23'OOs.
Mr. Lenehan llh. 55m. 36'34s.
"Woodford — Mr. Vessey llh. 55m. 14'96s.
These times show a very satisfactory agreement, especially when the
difficulty of seeing external contacts is taken into account, and the fact
that in 10 seconds of time Venus would only encroach about half a second
of arc on the sun's limb, a quantity not easily seen. For second contact
I think there can be no doubt that different phases of the phenomenon
were taken by observers according to the different effects produced by the
ghost of the black drop, which up to that time had a very tangible existence
for all of us, not only from what we had read about it, but from seeing it
so constantly in the artificial transit ; and as it is very important that the
exact phenomenon taken by each, observer as internal contact should be on
record, I will here quote from the reports, beginning at Eden.
Mr. Scott took the time when ' he saw the partial obscuration of the
sun's limb by the planet's atmosphere gradually diminishing until it dis-
appeared altogether at 12h. 24m. 48s.', which I take to mean the com-
pletion of the sun's outline, the same phase which, as will be presently
seen, I and others took for complete ingress.
INTRODUCTION. xiii
Mr. MacDonnell took the time when ' the light seemed to be going
in and out several times and prevented any accurate determination of com-
plete ingress as 12h. 25m. 14'7s., but he is convinced he was 15s. late,
making the time 12h. 24m. 59'70s.'
At Woodford, Mr. Vessey took the time when Venus appeared to
touch the sun's limb, or when the two limbs were tangential. (See
Plate II.) Time, 12h. 23m. 47 '07s.
My own report of this phase is as follows, and it will observed that
the first time given is 4 minutes before contact.
At 12h. 20m. Os. indications of distortion or bad definition of the
limbs in contact appeared, like a mass of black wool laid over the place,
rendering it impossible to see distinctly and making the cusps very hazy. (See
Plate XXVI.) I thought the drop was going to form, and watched very
closely for it and for apparent contact, but I found it extremely difficult
to make up my mind about the latter, and saw nothing of the former.
12h. 20m. 51s. was noted as a very unsatisfactory apparent contact. The
cusps after this appeared to clear up or improve in definition (the telescope
had not been altered), and as they approached each other the sharpness
was very remarkable, but the motion so gradual, that I could not deter-
mine to a fraction of a second when they actually formed the line of light
which I saw complete and took for the moment of internal contact, but
the instant I was sure I made the record on the chronograph, which was
at 12h. 23m. 59s., and keeping my eye steadily upon it saw it had in
fifteen seconds become an unmistakable band of sunlight.
Mr. Lenehan says at time of ingress there was an indistinct shading
between the supposed edge of the planet and the sun, which for some ten
or fifteen seconds before the time I quote later, kept me in a state of
uncertainty as to the true time of actul ingress ; the shading did not break
abruptly, but seemed to melt away in such a manner as to leave a doubt in
my mind of the exact time the planet passed the edge of the sun, but I
distinctly saw a clear band of light at 12h. 24m. 48'34s.
Mr. Savage says : ' The definition at this point being so very bad
between the limbs of the sun and planet, and the edges at contact so very
dark as to defy accuracy, as the planet advanced on the sun a little way
this shading still connected the planet with the sun's edge, but that portion
xiv INTEODTJCTION.
of it nearest to the planet showed indications of fading away gradually,
until at length it disappeared altogether without any sudden hreak what-
ever, and at 12h. 23m. 43'93s. a streak of light became visible between the
planet and the sun's limb.'
Dr. Wright noted ' 12h. 24m. 30s., but was qiiite sure this was
late, probably 30s., making 12h. 24m. Os., having lost true contact looking
for the black drop.' These times are :—
h. m. s.
12 24 48-00
12 24 59-70
12 23 47-07
12 23 59-00
12 24 48-34
12 23 43-93
12 24 0-00
Mean ... 12 24 18-00
But I think it is evident that only Mr. Scott, Mr. Vessey, and
myself have taken exactly the same phase here, and the mean of the three
results is 12h. 23m. 57'12s. ; the differences are too great to give a satis-
factory mean from all the observers, but if taken it is 12h. 24m. 18'OOs.
Perhaps some of the differences may be attributed to differences of tem-
perament.
EGRESS.
For the third and really most important phase we had all fortunately
learned to disbelieve in black drops, and during the photographic work had
time to think and talk over what had been seen at ingress, and we went to
our telescopes much better prepared for the Avork before us ; still the
difficulties were by no means gone, and the motion of the planet was so
exceedingly slow that a few seconds variation is, I think, a necessity.
It was unfortunately cloudy at Eden, but the Goulburn observations
now make up for it.
Captain Hickson saw internal contact 3h. 54m. 28'Ols.
Professor Liversidge 3h. 54m. 20'37s.
Mr. Tornaghi 3h. 54rn. 25'79s.
At Woodford, Mr. Vessey says 3h. 54m. 37'50s.
INTRODUCTION.
The circles of sun and planet tangential, and the
ring of light about its own thickness outside the limhs of
the sun.
My own time for this phase is 3h, 54m. 39'66s.
After a period of had definition my report says,
' the limbs recovered their perfect definition and were
clearly and steadily separated by a line of light which at
3h. 54in. 2G'3s. could not have been more than half a
second of arc in thickness, and then the same marvel-
lous definition continuing just when it was wanted. The
line gradually contracted to a scarcely visible thread, and
the limbs made contact. There was no sudden break,
nothing but the perfectly gradual motion of the one
disc over the other, both beautifully defined, and I saw
one overtake the other at 3h. 54m. 39'66s.'
Mr. Lenehan says the first apparent contact was
at 3h. 54m. 21'Gls., a little jumping ; afterwards, saw a
band or faint and narrow streak of light between the
limbs of planet and sun, which clearly showed me that
the time above given was too soon. I then waited
until I was absolutely certain contact was complete, at
3h. 54m. 46'Gls., but I feel confident this time is from
7s. to 10s. after true time, making the true time ... 3h. 54m. 39'61s.
Dr. Wright makes time of: contact ... 3h. 54m. 39'59s.
Mr. Allerding makes time of contact ... ... 3h. 54m. 35'00s.
Now at Goulburn at this time the wind had become very strong, and
produced a tremulous motion which would no doubt account for the times
being a little early, for it would not be possible under those conditions to
see a very fine thread of light, and we know that such was seen by
the observers who agree best. Mr. Lenehan's time also is known to be
late, and we have five times left of which the extreme difference is 4'66s.,
and mean 3h. 54m. 38'27s. ; and two at Sydney — my own and Dr. Wright's
— agree Avithin less than one-tenth of a second.
INTRODUCTION.
For last contact we have only three observations
which do not accord very well. At Woodford, Mr.
Vessey took the time as 4h. 23m. 52-OOs.
and says : " This observation appeared to he correct to a
small fraction of a second. The indentation on sun's limb
gradually contracted in width till within thirteen seconds
of time given, and it then seemed to contract longitu-
dinally till it became a small notch like a boiling indenta-
tion. This was seen steadily diminishing till it suddenly
flashed out, and the limb of the sun became perfect."
My own observation makes this ... ... .., 4h. 24m. 27'00s.
At this time the last sign of the planet on the sun's disc
was seen as the faintest possible mark, which then
disappeared, definition being for the time very good, and
the observation quite satisfactory.
Mr. Lenehan saw last and final contact at ... 4h. 23m. 49'61s.
the edge of the planet being then lost in the edge of the
sun.
My own observation of this phase does not seem to be supported,
but the larger aperture of the telescope I used, the 11^ inch reduced to 6
inches, and the steady motion by clock-work, probably explain the difference.
Turning, now, to the physical phenomena observed, there are several
of them very interesting and important that will repay a little consideration,
and first in regard to the black drop so called. The account of this phen-
omenon given by Mr. Stone, Astronomer Royal at the Cape of Good Hope,
seemed so thoroughly satisfactory that I fully accepted it, and in common
with nearly all observers, expected to see the planet distorted into a pear
shape as it left the sun's edge, " as if a stalk or ligament connected it with
the sun's limb " (see Mr. Hirst's observations) which broke suddenly ; a
phenomenon the exact time of which could have been easily determined, but
instead of this a set of wholly unexpected phenomena presented themselves.
As the planet encroached on the sun the cusps remained perfectly
sharp until near the time of contact of the limbs, when a curious hazy
appearance became developed, and rendered it impossible, in spite of all
efforts, to see exactly what was going on. Most, if not all the observers,
INTKODUCTION. xvii
thought the drop was forming, but close attention only revealed a gradual
disappearance of the haze until the sun's and planet's limbs were left
perfectly clear and sharply denned with a thread of sunlight between them.
Rev. W. Scott says, in reference to this point : — ' I continued to
watch the planet for more than three minutes, and saw the partial obscur-
ation of the sun's limb by the planet's atmosphere gradually diminishing
until it disappeared altogether.'
Mr. MacDonnell says : — ' As Venus proceeded the shadowy envelope
disappeared, except between the planet and the sun's limb, where it seemed
to fill up the space between them with faint rings concentric with the
planet's edge. There was no distinct rupture of this appearance, the light
seeming to go in and out several times.' Professor Liversidge says, ' A faint
hazy gray filament like a streak of smoke was momentarily observed between
the edge of the planet and the sun ; it was very obscure and illdefined.'
My own report for ingress is as follows, at 12h. 20m. indications of
distortion or bad definition of the limbs in contact appeared, like a mass of
black wool laid over the place, rendering it impossible to see distinctly, and
making the cusps very hazy. I thought the drop was going to form, and
watched very closely for it, and for apparent contact, but I found it
extremely difficult to make up my mind about the latter, and saw nothing
of the former. 12 hours 20m. 51s. was noted as a very unsatisfactory
apparent contact. The cusps after this appeared to clear up or improve
in definition, and as they approached each other the sharpness was very
remarkable.
At egress a curious phenomenon then presented itself similar to that
remarked at ingress ; the two limbs at the point of contact seemed to get
confused or badly defined, whether from atmospheric causes near us, or
some peculiarity about Venus, I am unable to say, but it seemed to disturb
the planet in a most remarkable way.
Mr. Lcnehan says, at the time of ingress there was an indistinct
shading between the edge of the planet and the sun, which for some
seconds kept me in a state of uncertainty as to the true time of actual
ingress ; the shading did not break abruptly, but seemed to melt away in
such a manner as to leave a doubt in my mind of the exact time the planet
passed the edge of the sun.
xviii INTEODTTCT1ON.
It is evident that what we have here described is a phenomenon
very different from that Avhich is known as the Mack drop, for here the
uncertainty lasts much longer, and does not occur when the limbs are
apparently separated, but when they are in fact, as well as appearance, in
contact, and slightly overlapping, and while this phenomenon is clearly
made out to have lasted about four minutes. Mr. Stone, Astronomer-Royal
at the Cape of Good Hope, and the best authority on this subject, estimated
that the black drop would only last 18 seconds.
Of the drop phenomena which we all expected to see we have two
particularly interesting accounts, which I will quote. The first is that by
Mr. Hirst, who was thoroughly acquainted with the phenomenon as
described by Mr. Stone and others, and had practised with the artificial
transit, though the work which was specially his, and of which he had
made himself master, was the management of the photo-heliograph during
the taking of the Janssen pictures.
Attached to the tube of the photo -heliograph was a finder consisting
of a single non-achromatic lens 1^ inch aperture and 4 feet focal length.
This was originally arranged by the maker so as to throw the sun's image
on to a piece of parchment fixed at its focus ; but in order to adapt it to
circumstances which required that one end of the heliograph should be in the
photographer's dark room, the lens was inserted in the end of a brass tube,
an eye-piece being provided in the shape of a Huyghenian combination,
giving a power of about 50 diameters. The chromatic and spherical aberra-
tion of the single lens were not obtrusive owing to its extreme focal
length, so that fair definition could be obtained of the edge of the sun,
and the existence of even minute solar spots made plainly visible.
Of the drop as seen with this, Mr. Hirst says : — To diminish the
light in the finder I used a thick piece of orange-coloured glass, which
gave an agreeable image of the sun. This was placed outside the eye lens
of the eye-piece.
I had prepared and placed a plate in the Janssen apparatus, when,
on taking my usual glance at the finder, to see that the telescope
was adjusted ready to take photographs, I observed the disc of Venus
appearing, as it were, rather more than one-third her own diameter within
the sun, and connected with the limb by a narrow line intensely black,
with an ill-defined edge. Plate XV represents the appearance as faithfully
as I can recollect ; this was about five seconds before No. 5 Janssen plate
INTRODUCTION.
was begun. I had not time for more than a glance, for I wished to pro-
cure a photograph of what I supposed to be the black drop, so universally
observed by astronomers, more than a century ago, at the last transit.
On getting the plate through, however, it showed nothing of what I had
so distinctly observed a few seconds before.
Referring to the finder, Vemis appeared well inside the sun, but
apparently nearer the limb than she seemed before. The drop was gone.
I thought at the time that it might have broken before the exposure of the
plate, and I determined to keep a sharp look-out for its formation at egress.
Soon afterwards Mr. Vessey came in and reported that the 4^-inch had
shown no drop at all.
Towards egress I referred constantly to the finder, that I might be
ready with a plate directly the drop became visible. When Janssen plate
No. 9 was in its place, and upon adjusting with the finder, I observed no
black drop, the planet appearing so far within the sun's disc that I did not
think it necessary to hurry in order to catch the drop and exposed the No.
9 plate, meaning to get another in time. After taking out the plate, which
probably occupied twenty seconds, I went to the finder, and to my astonish-
ment saw that the drop had formed, appearing about as long as one-third
the diameter of the planet. I hurried on the next plate as much as
possible, but a delay unfortunately of a couple of minutes occurred before
it was ready ; on development it showed Venus a perfectly circular disc
touching the sun's limb. It appears in Mr. Hirst's report of egress that
the interval in time between actual contact and his seeing the black drop
was 1m. 45'41s., almost exactly the same time as ingress.*
I regret exceedingly that my eye was not at the finder during the
precise moment of the formation of the drop, but my duties at the Janssen
apparatus prevented me from staying there more than a few seconds at a
time.
* The exposure of Janssen plate No. 9 was begun at 3h. olm. 42'42s.
And it was finished at 3h. 52m. 31 '39s.
Mr. Hirst took out the plate and looked in the finder and saw the Mack drop as
described at 3h. 53m. 3s.
Mr. Vessey in the next tent observing with a first-class 44-inch equatorial saw no
drop, and contact did not take place until (Mr. Vessey's report) 3h. 54m. 48'41s.
hence it appears that at 3h. film. 42'92s. there was no visible black drop at 3h. 53m. 3s., the black drop
was visible through the finder of the photo-heliograph ; while it appears from Mr. Vessey's observations that
actual contact as seen with a good telescope did not take place until 3h. C4m. 48'41s., so that the black drop
was seen with the imperfect telescope 1m. 45'41s. before contact, and may have been visible a few seconds
earlier.
xx INTRODUCTION.
Referring to what I saw through the finder I am convinced that
my observations, short though they were, have not deceived me. I was
thoroughly prepared, and on the look-out for the phenomenon at egress,
and I have not the slightest doubt that any one, using similar optical
instruments, would undoubtedly have observed what I did.
If we turn now to No. 5 Jarfcsen plate (plate XIV) and seek a photo-
graph of the drop, we find that photography, at least when aided by Mr.
Dallmeyer's beautiful lenses, refuses to acknowledge any such phenomenon ;
on this plate there are sixty photographs without a sign of the drop, but
all showing a distinct band of sunlight round the planet. It will be
remembered that while this was going on in the photo-heliograph obser-
vatory, Mr. Vessey was in the next place observing the phenomena of
ingress with a very fine 44-inch equatoral, by Schroeder. With this in-
strument a splendid view of the ingress was obtained, and he noted internal
contact at 12h. 23m. 45'07s. No. 5 Janssen plate was begun at 12h. 25m.
35'47s., and Mr. Hirst saw the drop 5s. before this, or at 12h. 25m. 30s.,
or some time after ingress had taken place, and it appeared to him equal
to rather more than one-third of the diameter of the planet. Now
we know it was only 1m. 45s. after observed ingress, and the photographs
prove that the planet was only 1-22 part of its diameter within the sun's
limb.
Of course there is the possibility that the drop might have broken
between the time when Mr. Hirst saw it through the finder of the
photoheliograph and the tune he began to turn the handle of the Janssen
apparatus on the same instrument ; and the time lost in this change could
not possibly exceed 5 seconds, for he passed from one to the other as
quickly as possible, and even if it did break, we have the facts clearly
made out that the drop was seen 1m. 45s. after ingress, and that although
it appeared nearly equal to the one-third of the diameter of the planet in
length, yet it was certainly not more than l-22nd of the diameter as
shown by the photograph.
Mr. Allerding, chronometer maker, of Hunter-street, also saw the
drop most distinctly, and watched it through the various phases till it
broke. He was using at the time a very good 3^-inch achromatic
telescope, but to avoid sunlight and heat he had reduced the aperture to
two inches, and with this small opening he obtained very satisfactory
INTRODUCTION. xxi
definition of the sun and planet. Unlike Mr. Hirst, who observed in the
beautiful atmosphere of the mountains, Mr. Allerding observed from the
back yard of his house in Hunter-street, which is surrounded by houses.
In a report of his observations, which he has furnished to me, he says : —
' At the internal contact at ingress, I saw a drop which formed into a
cone, and when this had nearly disappeared it seemed to stretch out to a
fine thread (see plate XIII), to which Venus seemed to be attached. The
thread appeared hard and definite, without any hazy margin, and I
estimated its length at one-third the diameter of the planet. It then instan-
taneously disappeared at 12h. 24m. 44s., and Venus appeared already
well detached from the sun's limb. Had I not waited for the disappearance
of the fine line, I would have made inner contact at least 30 seconds
sooner.' The mean of the time for internal contact given by 7 other
observers in Sydney is 12h. 24m. 23s. Mr. Allerding made it 12h. 24m.
14s. Now, in this case we have no Janssen photographs to show how
long the drop was, but my own observation taken in Sydney proves that
the drop seen by Mr. Allerding was equal in length only to the space
moved over by the planet in 45 seconds, that is, 1'7 seconds of arc from
the sun's limb — that is, 2^ times the length Mr. Stone estimated it to be.
In New South Wales, therefore, only those who were using tele-
scopes of small aperture, 1^ and 2-inch, and low power eye-pieces saw the
black drop ; and one, Mr. Hirst, was in a remarkably clear and steady
atmosphere, and Mr. Allerding in a very unfavourable one, owing to
the radiation of heat on a hot day from all the houses around him. So
far then as this evidence goes the black drop does not seem to be due to the
atmospheric conditions, but rather to the imperfections of telescopes of
small aperture and low power.
'There are, however, several observations recorded of a kindred
phenomenon that I should like to place on record. At ingress I saw
nothing of it, but at egress I saw it distinctly ; and the cause is, I think,
easily traced. But to take, first the observations at ingress.
Messrs. Belfield and Park, who were observing at Armidale with a
4^-inch Cook telescope, that I examined, and know to be a good one, have
sent me a valuable report and drawings of what they saw, and state that
' while Venus was advancing at ingress to about one-fourth her own
diameter upon the sun, a faint tremulous shaking was seen between the
xxii INTRODUCTION.
limb of the sun and the planet (both bodies being very sharp in outline),
which disappeared so gradually that it could not be said to have been
obliterated at any particular instant. (Sec plates IX and XX.)
Mr. Bolding, P.M., Raymond Terrace, observed with a 3-inch tele-
scope, and has forwarded to me a very complete report of the whole transit,
and remarks: — 'At the moment I expected the complete circle (i.e.,
internal contact) came the apparent pause, instantly followed by a kind of
indistinctness, which resolved itself into the form of a figure 8. The thing
seemed to be holding up the planet, so to say, and appeared as represented
in plate XXVIII, diagram 3. The line seemed blacker than the central
spot ; then the light came very distinctly between the planet and the line ;
then the indistinctness between the sun's limb and the line cleared up, and
for a short time the line was clearly seen midway between the planet and
the sun's limb. The sun was very hot at the time, and the definition bad.'
Mr. Russell : At ingress I saw nothing of the phenomenon, but
at egress I did, and my report is as follows : — ' At times there were moments
of bad definition, evidently caused by the clouds then forming in the west.
During one of these, at 3h. 53m. 54s., when Venus was less than two
seconds of arc from the sun's limb, the limb of the planet nearest the sun's
edge seemed to be in a state of vibration, as if portions of its blackness
were jumping over to the margin of the sun with an appearance similar
to sketch which represents one vibration only. This lasted only a few
seconds — the vibrations being estimated at six or seven per second.
After this the limbs recovered their perfect definition, and were
clearly and steadily separated by a fine line of light. Mr. Lenehan saw it,
and says, ' The first apparent contact was at 3h. 54m. 22s., a little jumping.
I afterwards saw a band or faint and narrow streak of light between the
limbs of planet and sun.'
Messrs. Belfield and Park saw the same appearance at egress as at
ingress. Mr. Bolding saw nothing of it at egress, which he attributed to
the increased steadiness of the atmosphere.
I think there can be no doubt that this appearance was caused by
temporary unsteadiness in the atmosphere, which, by' producing rapid
vibrations or apparent motions in the limbs under examination, caused
INTRODUCTION.
them momentarily to overlap, and so cut off the sunlight and produce the
black appearance, an effect which all who have been in the habit of
observing with powerful telescopes will at once understand.
We come now to the last point that I propose to speak of. The
information I have collected about it is in some respects very remarkable.
I refer to the rings of light and especially the halo seen surrounding the
planet Venus, a conspicuous phenomenon seen by nearly all the observers
in New South Wales. That it was a very brilliant and beautiful object
will be made abundantly evident by the accounts which follow.
And beginning, as before, with Eden. Mr. Scott, who was using
a 7^-inch equatorial, of very fine defining power, and of which the
aperture was reduced to two inches, says : — ' For some minutes
before internal contact I could see clearly at ingress the whole of
the planet's outline; in fact, it presented exactly such an appearance
as might have been expected from a planet possessing an atmosphere.'
Mr. MacDonnell says : — ' At the time of apparent bisection, a shadowy
nebulous ring seemed to envelop Venus (see plate XVIII ; on the
preceding side it was of lighter tint than the planet, but was decidedly
perceptible, and appeared to be about one-quarter or one-fifth of the
diameter of the planet in width. When ingress was about two-thirds
completed, the whole outline of the planet was distinctly visible in the
telescope, the shadowy envelope surrounding it very plainly.'
At Goulburn, Captain Onslow first saw the halo, or ring of light, at
12h. 17m. 5s. A bright light was seen at the lower point of intersection
of the circles (see diagram plate I, figs. 1 and 2), and in a few seconds
a similar one at the upper point, and at 12h. 19m. 5s. an apparent circle
was formed by the planet.
Professor Liversidge says, when the planet was about one-third of
its diameter from third contact : — ' It then appeared spheroidal, and not
as a disc merely (see plate XXII, figs. 1, 2, 3) ; it appeared illuminated
on the under side in the direction of the sun's diameter, or on the side of
the planet towards the sun's centre, and this illumination shaded off on
each side of the planet, but at the portion nearest the sun's limb it appeared
quite black and opaque. This globular appearance was retained until the
planet had passed off the sun's limb to the extent of about one-sixth of its
diameter.'
INTRODUCTION.
' After internal contact, the planet looked somewhat as if it were
pushing that portion of the sun's limb hefore it, for the solar limb appeared
to be raised up into two processes — one on each side (plate XXII, fig. 6) .
At the time I thought it might, perhaps, be due to an -atmosphere sur-
rounding Venus, or to an optical illusion ; but since I have heard that
other observers saw the illuminated edge of Venus beyond and outside the
sun, I am inclined to think it was that which I saw. However, I did not
see a circle, but merely two portions or cusps brightly illuminated, but not
as bright as the sun.'
At Woodford, Mr. Vessey, who had the best atmospheric conditions
and a first class telescope, saw so much of the shading on the planet and
the halo that it would not be possible to reproduce all he says without
extracting greater part of a long report. The shading on the planet was
first seen at 12h. 7m., but not on the part off the sun; it appeared to extend
inwards from the limb, resembling a gradually fading line of dots.
At 12h. 15m. 30s. the following limb of Venus was distinctly defined
by a faint line of light or halo which was rather brighter on the northern
side ; 3 minutes later ring of light increasing in beauty, silvery, decidedly
brighter on north side of middle, perhaps ^ a second in thickness.
After complete ingress the definition was magnificent (see plate I,
No. 3), and atmospheric ring or shading on, i.e., within the disc of the
planet similar to what I first saw at 12h. 7m., but broader, and gradually
shading off towards the centre, to be traced all round, giving Venus an
appearance of relief like an oblate spheroid, or rather a flattened dome
standing away from the sun, the radius of the flattened part being about
half that of the planet.
At egress Mr. Vessey again saw the ring of light directly contact
was made, and steadily as the planet proceeded, at first like a small arch
upon the sun's limb at 4h. 2m. 35s., the ring of light on planet appeared as
a sharply defined line, and less than one second of arc in thickness, 6
minutes later, disc of Venus still continues undoubtedly a globe, and
appearing slightly reddish or copper coloured (plate I, No. 4), like the
moon in an eclipse, the sky adjoining intensely black, with the suspicion of
a greenish tinge contrasting with the colour on the planet.
INTBODTICTION. xxv
Mr. Du Eaur, observing at Woodford with a 3-inch telescope, the
eye-glass of which (after being smoked) was cracked by the sun, and there-
fore in a very unsatisfactory state for observations, still saw the whole of
the planet when it was about two-thirds on the sun ; and during the interval
between internal contacts, had frequent opportunities of observing Venus
with a 4J inch telescope after it had been carefully focussed on the sun
spots, and saw Venus as sharply defined as it would be possible to
represent it on paper, and perfectly black.
Mr. Russell says, 'At ingress I did not see the halo or ring of light
round the planet (plate XXVII, fig. 3.) until 12h. 16m. Os. It appeared
only round that part of the planet not on the sun. It was very remarkable
and beautiful, like a fringe of green light, through which the faintest
tinge of red could be seen. It was densest near the planet, and seemed
to shade off to nothing with a diameter estimated at one second of
arc. It did not appear solid like the disc of the sun ; but, like light in a
dense vapour (see plate XXX), as ingress proceeded, the halo became
more conspicuous ; but I did not observe any want of uniformity in its
diameter. At egress I saw nothing of the halo until 3h. 57m. 7s., nearly
2^ minutes after internal contact. The halo was exactly similar to that
seen at ingress, and the whole of the planet at this time appeared to me
intensely black. The halo remained steadily visible for some time, but
gradually faded, owing to increasing cloud causing a great increase in
brightness of the atmosphere about the sun ; and at 4h. 6m. 52s. I first
observed that the surface of Venus was not black as it had been, but
appeared as if covered with thin hazy clouds, somewhat thicker on the
planet's northern hemisphere. At this time, the haze having much
increased, I lost sight of the halo, and at 4h. 12m. changed the coloured
glass for one of lighter tint, and at once saw the halo again, and for the
first time noticed that it was irregular in diameter ; it seemed considerably
broader at the north pole of the planet and shaded off more rapidly towards
B than C (see plate XXV, figs. 2, 3, 4, and 5), but I found it impossible to
look at the sun steadily with this light glass, and again changed it for a
darker one, when all the halo, except the part at the north pole, disappeared;
this white patch continued visible against the sky (fig. 5.) until within one
minute of last contact, and I feel confident I should have seen it some
time after last contact but for the rapidly increasing atmospheric haze,
which had also much increased on the planet, making it difficult to see
where the haze on the planet ended and the sky haze began.
d
xxvi INTRODUCTION.
Mr. Lenelian says, ' At 4h. 16m. 21s. the planet appeared with tlie
outer edge apparent, and I noticed a spot of light on the preceding side as
at A. (See plate XVII, fig. 4.) It did not appear to me as anything more
than a spot.'
Messrs. Belfield and Park saw the following limb of planet at ingress
distinctly illuminated, and when the planet was wholly on the sun the
body of the planet appeared intensely bluish black in centre, becoming
gorgeous (see plates VIII, X, and XXI) deep blue towards the circum-
ference ; at egress the illumination of the planet's limb was again seen, but
only on the north side.
Mr. Bolding only saw the halo at egress, and though visible all
round that part of the planet off the sun was most marked on the north
side. (See diagram, plate XXVIII.)
It will be seen that we have here three distinct phenomena. A
broad ring of light outside the planet, a bright ring of light round that part
of the planet projected on the sky, and band of light or shading round the
inner edge of the planet, or over its surface. No spots, however, were seen
on the planet, except the very remarkable part of the halo at the north pole.
The cause of the halo seen by Messrs. Lenelian and MacDonnell has
not been satisfactorily made out, though it has been repeatedly seen during
transits of Mercury. It seems exceedingly improbable that Venus has an
atmosphere of such extent as would be required to produce such a halo or
ring of light as that seen by both these observers. It appears, however,
certain that it is one of those curious phenomena seen only by some observers
under special conditions. The transit of Mercury in 1868 was watched
very closely by a number of observers in England, who were seeking
information that might be useful for the transit of Venus; and out of four-
teen observers, including some of the best in England, only three make any
mention of the diffused exterior halo. Mr. Stone thought it simply an
effect of contrast.
Probably some of the light seen on the planet this time had a
similar origin, no observer has, so far, reported seeing both. A part of it,
however, must, I think, be attributed to haze in our own atmosphere,
which, being very luminous owing to moisture then forming, would appear
projected on the black planet, and the contrast would very likely give it a
INTRODUCTION. xxvii
shaded appearance from the edge towards the centre. To me the blackness
of the planet, both at ingress and egress, was very intense, until the haze
in our atmosphere became thick and gave the surface of the planet a cloudy
look, so that I could scarcely see where the planet ended and the sky
began ; and it may be that the same cause produced what Professor
Livcrsidge and others saw ; but at Woodford the air was too clear for such
an explanation. The red tint seen by Professor Liversidge is explained by
his having used a red glass shade.
The increase or thickening of the halo seen at the north pole of the
planet, and which to several of the observers seemed to encroach on the
planet, is a most interesting feature, especially if taken in conjunction with
an apparent flattening of the planet, seen by Mr. Vessey at the opposite side.
The remaining ring of light or halo is the most interesting physical
feature observed, though at first sight it would be attributed to an atmos-
phere similar to that of the earth. I think a little consideration will show
that it cannot have such an origin. It is spoken of by all the observers as
very brilliant, by some as white compared with the sun ; and its actinic
power was so great that, although its diameter was certainly less than one
second of arc, and would only appear as a fine line in a Janssen photograph
less than one five-hundredth part of an inch in diameter, it yet had pawer
to effect the chemicals more than the sun itself in something less than the
two hundred and fiftieth part of a second ; in other words it was more
powerful in affecting the silver salts on the photograph plates than direct
sunlight, and we have a number of Janssen plate photographs in which
it is shown by a deposit of silver thicker than that made by the sunlight.
This great brilliance, of course, explains why it was not seen about
the planet while on the sun's disc. It was evidently not to be distinguished
from the sunlight.
In the clear atmosphere at Woodford, it was seen as soon as the cusp
parted at egress, and it will be exceedingly interesting next time Venus is
lost in the sunlight to try if, under favourable conditions, his halo can be
seen. Quite sure I am that, if the air had been clearer at egress, I should
have seen the planet with the halo round it projected upon the sky, as it
was I saw part of the halo until Venus was nearly all off the sun's disc, and
one minute before last contact. Taking all these facts into consideration,
I cannot see any cause sufficient to produce a halo or a ring of light such
xxviii INTEODUCTION.
as that described, an atmosphere by refracting, would diffuse the light and
by absorption would reduce it, so that the halo cannot be the result of an
atmosphere.
Some of our Janssen plates give results which are obvious enough
without measurement ; one of these is the extreme sharpness of all the cusps.
Of the sixteen plates having about sixty photos on each — the first plate
shows a small notch in the sun's limb ; Nos. 2 and 4, planet still further in ;
No. 5 is the one taken when the black drop was seen ; No. 6 shows the
planet wholly within at ingress 7, 8, and 9, the same at egress ; No. 9-£- shows
the planet on the sun's limb, with the halo ; No. 10, planet partly off sun,
with some pictures of the thickening of the ring of light about the pole of
the planet ; Nos. 11 to 16 plates, at egress ; No. 17, was passing through
when last contact was observed, and shows the faintest notch in the sun's
limb till within a few seconds of observed last contact. The value of these
plates is very great ; photography is not biassed by preconceived theories
of what it should see, and is therefore a witness upon questions of physical
aspect whose evidence no one may gainsay.
On February 22nd, 1875, I left for England, taking full copies of all
the reports and observer's drawings, together with ten Janssen plates, each
having sixty pictures of a portion of the sun with Venus near the limb, and
fifty-seven photographs of the sun four inches in diameter, some taken at
Sydney and others at Woodford ; these were all given to the Astronomer
Royal for England, on July 14th, 1875, as the New South Wales contri-
bution towards the observation of the Transit of Venus, and in January,
1876, others were sent, making up the numbers to 109 Sydney 4-inch
plates and thirty-six Woodford plates, and twelve Janssen plates, some of
these not having quite the full number of photographs on them.
The observations will be found very fully illustrated, and other
plates have been added showing Sydney observatory, the temporary obser-
vatories used at other places, and also, the larger instruments, tents, &c.
Unfortunately, Goulburn buildings were taken down before a photograph
of them was secured and the only one of the large instrument is very
imperfect but it is the best available.
H. C. RUSSELL,
Sydney Observatory, Government Astronomer.
16 August, 1892.
MR. RUSSELL'S REPORT re TRANSIT OF YENUS.
Sydney Observatory, 9 December, 1874.
THE early morning was clear and fine, but from 5h. 30m. a.m. to 8 a.m. The weather.
thick fog-like clouds covered the sky ; they seemed to be very low down,
and all melted away under the increasing heat, leaving the sky beautifully
clear and promising for the work before us — a promise which was fully
realized during the day.
All the observers were at work early, giving finishing touches to our Preliminaries,
preparations, and giving and receiving clock signals to ensure accurate
time. At Sydney this occupied a considerable time, for three stations —
Eden, Goulburn, and Woodford — required the signals, and some were
given to private observers. By 11 a.m., however, all this was over, and
all the telescopes and photographic apparatus for use in Sydney were quite
ready for the work, and the observers had time to look quietly over the
preparations and see that all was ready.
The principal instrument was the new Equatorial by Dr. Schroeder, instruments.
of Hamburgh, which had been obtained for the purpose of observing this
transit. It has a clear aperture of 11'4 inches and a focal length of 12 feet
G inches, and was provided with a full battery of eye-pieces, and a polarizing
apparatus for viewing the sun. The definition of this instrument is superb,
with the new achromatic eye-pieces supplied by Dr. Schroeder, but owing
to the great heat concentrated in the focus on that bright summer clay, it
was found necessary to reduce the aperture to five inches when observing
and six inches when photographing. Eor the purpose of taking photo-
graphs it was fitted with a camera and enlarging lenses of such power that
the sun's image measured four inches. The photo plates were placed simply
at the end of the camera and held by a spring while the picture was taken,
no dark box being necessary, because the camera end of the telescope
passed into the dark room, which was simply a tent raised inside of the
dome and connected with the telescope by means of a flexible sleeve, so
that the telescope was free to move with the clock-work. A flashing
bd 35—92 A
2
TBANSIT OP VENUS.
Distortion.
Enlarging
lenses.
shutter of the ordinary kind was used, and when the plate was in position,
a very light spring was touched, set the shutter free and made a picture; which
was immediately removed and developed, and as soon as it was washed, the
shutter was lifted, and the camera ready for another. This precaution was
necessary, because the shutter in its motion upwards, which was of course
by hand, and comparatively slow, let a flash of sunlight into the dark
room. Thus arranged it was found that three persons could and did work
at the rate of one photo per minute, with the ordinary wet collodion process.
One coated the plates and put them in the baths, of which four were used,
fixed on a turn-table, so that by the time a plate had travelled round it was
sensitized. The second worker took the plate out and put it in the camera,
exposed it, and handed it to the third, who developed it and finished the
picture ; this duty devolved upon me, and I was thus able to see during
the progress of the work that the plates were properly exposed, and that
the driving-clock kept the sun's image on the middle of the plate.
Attached to the flashing shutter apparatus was a contact-maker and two
wires that led to the chronograph ; every flash of the shutter was thus
recorded, and against each record on the tape the number of the plate
exposed was written, which thus furnished an exact record of the time of
exposure, the plates being identified by numbers written on them with a
diamond beforehand. The same chronograph was vised for recording the
times of the various phenomena observed.
Before I leave the instrument, it is necessary to say that the
enlarging combination was of peculiar construction. It had been found
that the ordinary enlarging lenses, and especially the one made for this
telescope, gave to the limits of the field considerable distortion. To get over
this difficulty experiments were tried, and it was found that two plano-
convex lenses of equal focal length placed convex sides towards each other
could be so adjusted that there was no distortion of the field ; in fact a
large white screen was carefully ruled into inch squares and placed four
hundred feet from the telescope, when photographed, all the lines were
straight. This combination was therefore adopted for the transit work, and
all the Sydney photos were taken with it.
As a proof of its accuracy, the Scale of Inch squares was set up at a
distance of 400 feet and a photograph of it taken, from which by direct
printing the photo herewith was produced. (See plate xxxn.) An inspec-
tion of this shows that there was no distortion, or in other words, the field
was quite flat.
TEANSIT OP VENUS. 3
The camera was so made that it could be put on or off the telescope
in one minute. Before ingress the telescope was placed ready with a direct
vision achromatic eye-piece magnifying 100 times, and the coloured glasses
were a green one before the eye-piece and a dark blue or neutral shade near
the eye ; so protected, no inconvenience was felt from the sunlight. Other
magnifying powers were tried, as was also the polarizing eye-piece; but the
observations were made at ingress and egress with the 100 eye-piece
described above. The telescope was clock-driven, so that my whole
attention was given to the work of recording the times of contacts at
ingress and egress, and to secure accuracy a chronograph on which the ticks
were marked by the standard clock was used, and against each mark made
by the observer, an explanatory note was made on the paper tape by the
assistant in charge of the chronograph ; and in order to guard against the
total loss of the observation by failure in the electrical contacts, I had a
chronometer near me and recorded the time to the nearest second by it.'
These notes served also as a check on the chronographic work.
The error and rate of the chronometer were found by comparison
with the standard clock before and after the observations, and the error
and rate of the standard clock were found by transit observations the
nights before and following
As soon as I had observed the phenomena of ingress, the eye-piece
was removed and the camera put in its place, and we commenced to take
photographs of Venus in transit, and during 3 hours 10 minutes 190
pictures were taken.
The observations at ingress.
At llh. 40m. a.m.* I began to observe, and adjusted the focus very
carefully, so that spots and faculac on the sun's surface could be seen
distinctly, and then a close watch was kept on that part of the sun where
the planet was expected. I was surprised I could see nothing of the planet
at llh. 54m., but kept my eye steadily upon the place, and at llh. 55m. 23s. First contact
saw the first sign of Venus certainly on the sun. I thought that the
indent I saw was the planet a few seconds before, but could not be sure
it was not one of the irregularities in the sun's limb due to atmospheric
causes, until about 15° of the planet's circumference were in contact.
Probably the time should be 10 seconds earlier. From this point until 5
minutes past 12 (noon) there was nothing to remark but the sharp and
definite outline of the planet as it crept over the sun. At this time, 12h. 5m.,
* All the times given in this and other following reports are in Sydney mean time.
4 TRANSIT OF VENUS.
Planet all the Avhole of the planet became visible (plate XXVII, fig. 1), that portion
of it Avithout the sun appearing on the bright sky near the sun's limb ; as
ingress Avent on, the planet became more and more distinct, and seemed to
stand in relief on a back ground of greenish grey light (fig. 2). It Avas
uniformly black, and I could not detect any haziness about its outline on
the sun, except during moments of bad definition, Avhich AA'ere temporary,
and evidently due to changes in our own atmosphere. The outline of the
sun and the cusps were also sharp, but I Avould not be certain that the
halo afterwards noted was not then visible.
Halo. At 12h. 16m. I first observed the halo (plate XXVII, fig. 3) ; the
planet had been getting gradually more conspicuous both on and off the
sun's limb, and my attention had been principally directed to the cusps, to
detect, if possible, any phenomena like the formation of the D-shape, but
nothing Avas seen, and when taking a general look at the time noted, I
'first observed the halo round that part of the planet not on the sun. It
Avas very remarkable and beautiful, like a fringe of green light, through
Avhich the faintest tinge of red could be seen ; it AAras brightest near the
planet, and seemed to shade off to nothing, with a diameter estimated at
one second of arc. It did not appear solid like the disc of the sun, but like
light in a dense vapour. As ingress proceeded the halo became more
conspicuous, but I did not observe any Avant of uniformity in its diameter,
and it at all times terminated at the sun's limb, there being no sign of the
halo on the part of the planet on the sun.
Plate XXX is an attempt to show what Avas seen, but the halo is far
too broad, and I Avas unable to put on paper Avhat I saAAr.
Bad definition At 12h. 20ni. indications of distortion or bad definition of the
limbs in contact appeared, like a mass of black AVOO! laid over the place
(plate XXVI), rendering it impossible to see distinctly, and making the
cusps very hazy. I thought the drop Avas going to form, and Avatchcd
very closely for it and for apparent contact ; but I found it extremely
difficult to make up my mind about the latter, and saw nothing of the
former.
Apparent 12h. 20m. 51s. Avas noted a very unsatisfactory apparent contact.
The cusps after this appeared to clear up or improve in definition,
and as they approached each other the sharpness Avas very remarkable,
but the motion so gradual that I could not determine to a fraction of a
second Avhen they actually completed the line of light ; but the instant I
conS! was sure I made the record on the chronograph, for "internal contact";
TEANSIT OP VENUS.
the time was 12h. 23m. 59s., and keeping my eye steadily upon it, saw it
had in 15 seconds become a distinct and unmi stateable band of sunliglit.
The planet and its neighbourhood were then examined with great care, and
presented a perfectly black unmarked surface, with a hard and distinct
outline, and near it nothing but the uniform light of the sun could be seen.
Observation was then (12h. 30m.) given up, and the camera put
upon the telescope, and in the course of 3 hours and 10 minutes 190 photos
were taken. Four of these are useless from accidental causes, but on the
remainder is a clear and beautiful record of the planet's progress across
the sun.
Egress.
At 3h. 40m. p.m. we gave up taking photographs and prepared for
observations. The same eye-piece and coloured glasses were used. The
planet now had a perfectly sharp and clear outline, that of the sun being
also very good. I could not after careful scrutiny see anything remarkable
on the margin of or near the planet, and the limbs continued to approach
each other beautifully denned (plate XXIV fig 1) . Great care was exer-
cised to keep a steady watch without straining the eyes. At times there
were moments of bad definition, evidently caused by the clouds then
forming in the west. During one of these, at 3h. 53m. 53'59s. the limb of Jumps,
the planet nearest the sun's limb seemed to be in a state of vibration, as if
portions of its blackness were jumping over to the margin of the sun with
an appearance similar to fig. 2, plate XXIV, which represents as nearly as
can be estimated the space over which the phenomenon was seen as com-
pared with the diameter of the planet. This lasted only a few seconds, the
vibrations being estimated at 6 or 7 per second; after this the limbs
recovered their perfect definition, fig. 3, plate XXIV, and were clearly and
steadily separated by a line of light, which at 3h. 54m. 26'30s. could not have Fine line of
been, more than half a second of arc in thickness ; and then the same mar- ''
vellous definition continuing just when it was wanted, the line gradually
contracted to a scarcely visible thread (fig. 4), plate XXIV, and the limbs internal
made contact at 3h. 54rn. 39.66s. There was no sudden break — nothing but C°
the perfectly gradual motion of the one disc over the other, both being
beautifully defined, and the observer saw one limb overtake the other. I
have no doubt that had the bad definition continued, the moment when the
jumps were seen would have been taken as the formation of the drop.
A curious phenomenon then presented itself similar to that remarked
at ingress, — the two limbs at the point of contact seemed to get confused or
TRANSIT OF VENUS.
Appareut
contact.
Halo.
Clouds on
planet.
badly defined, whether from atmospheric causes near us or from some
peculiarity about Venus I am unable to say, but it seemed to distort the
planet in a most remarkable way (plate XXV. fig. 1, and plate XXVI).
And now, as at ingress, I found it very difficult to determine apparent
contact, or what under the strange effect, seemed like the phenomenon
known by that name.
At 3h. 55m, 45s. it appeared to me that if Venus could be made
round it would be just in contact with the sun's limb. I took particular
note of the circumstance, in the hope that it would throw some light upon
the so-called black drop.
I did not at this time observe any halo or anything to indicate the
exact position of the planet's margin, and it was not until 3h. 57m. 7s-
(plate XXV, fig. 2 at B) that I saw the outline off the sun with the halo round
it exactly similar to that seen at ingress, and now as then only on that
portion of the planet which was off the sun. The whole of the planet then
appeared to me intensely black (as at A, plate XXV, fig. 2) ; at 3h. 59m. 12s.
the planet was all visible and the cusps very sharp ; 2| minutes later the
halo was only just visible ;, at 4h. 3m. definition bad, and the bright haze
about the sun noted to be on the increase. Definition improved again*
and at 4h. 6m. 52s. I first observed that the surface of Venus was not
uniformly black as it had been, but appeared as if covered with thin hazy
clouds, thicker somewhat on the planet's northern hemisphere, but nowhere
sufficiently dense to prevent me from seeing the dark planet at the back,
at least such was the impression formed at the time ; at 4h. 12m. thc
definition again became bad. Since the last note about the halo it had
almost disappeared, and I changed the dark blue shade for one of a lighter
tint ; with this saw the halo distinctly all round the part off the sun, but
could not look steadily at the sun, the light being too strong ; the halo
was for the first time seen irregular — in diameter it seemed considerably
broader at the north pole of the planet as shown (fig. 3, plate XXV, at A),
and shaded off more rapidly towards B than C. At 4h. 15m. 20s. (plate
XXV, fig. 4), the dark glass having been replaced, this northern band of
light was all that was visible of the halo, and the haze on the planet was
greater ; at 4h. 16m. 2s. the cusps were not sharp but rounded off ; the
appearance was coincident with another turn of bad definition, and the
atmosphere became now so much disturbed that there was little hope of a
satisfactory observation of last contact. The white patch on the planet had
however continued visible since it was first seen, though at times it became
TRANSIT OP VENUS.
very faint ; by its aid I was able to make out the outline of the planet, now
a very difficult matter, for the haze on the planet had become almost as
bright as the sky, and must I think have been due to the moisture gathering
in our own atmosphere.
At 4h. 22m. 12s. the white patch was distinctly visible ; definition white siiii
good again; faintly seen at 4h. 23m. 22s. (plate XXV, fig. 5), and at 4h. 24m. T'
27s. the last sign of the planet on the sun's disc was seen as the faintest Last contact,
possible mark, which then disappeared ; definition being for the time very
good, the observation was quite satisfactory. After this I tried to sec the
white spot on the planet but failed, as the haze in the sky was rapidly
increasing.
At this time the whole sky was very hazy, and long tapering clouds
were coming up from S.W., and I have no doubt the moments of bad
definition were caused by the passage of the points of these clouds across
the line of sight.
H. C. RUSSELL,
Government Astronomer.
Sydney Observatory,
9 December, 1874.
8 TEANSIT OF VENUS.
Copy of Memoranda on Cards used during observations.
INGEESS :—
NOOX. Planet perfect black clear outline (i.e. on sun).
h. m. s.
12 4 0 Planet very clear and sharp, nearly bisected.
12 5 0 Can see the whole of the planet, but not clearly.
12 10 0 Whole of planet plainly visible on a back ground of faint grey light.
12 15 0 Still visible outside sun ; planet's edge seems perfectly sharp ; just a shadow
of uncertainty about edge, think it is atmosphere.
12 16 0 All visible, at times beautifully ; no small body near Venus ; cusps perfectly
sharp. (Halo was marked on chronograph at this time.)
EGEESS :—
3 54 39'66 First contact ; sharp contact of limbs; 40s. later distortion about the point of
contact.
Venus looked in apparent contact with sun's limb.
3 57 7 Venus' margin off sun clearly seen with halo round it similar to that seen at
ingress.
. 3 59 12 All planet visible ; parts on and off the sun, latter with halo round it.
4 0 22 All visible, but halo not distinct : bright margin off sun not so marked.
4 1 42 All visible, but only faintest halo.
4 2 52 Planet's margin all visible off sun ; not well defined ; haze about sun seems to
be increasing.
4 5 12 All visible ; sun's edge very steady in glimpses.
4 6 52 Venus does not look uniformly black on north side — it looks as if planet was
cloudy.
4 8 52 All Venus visible.
4 10 52 All visible.
4 11 52 Bad definition, but all planet visible.
4 12 52 (Changed sun-shade to lighter one.) All visible ; halo distinct, specially on
the north side.
4 15 12 (Dark glass again.) Halo on north side only— it is very remarkable.
4 16 2 Cusps not sharp — seem rounded off.
4 17 42 White place still faintly visible ; white haze increasing.
4 18 52 Definition getting very bad — can still glimpse white spot by its aid follow the
outline of the planet.
4 20 32 Still visible, but very faint.
4 22 12 Can still glimpse it.
4 23 22 Doubtful (glimpses).
4 24 27 Last contact ends, definition good.
4 25 52 Certain I can see nothing outside sun.
II. C. EUSSELL,
Government Astronomer.
TEANSIT OF VENUS. 9
REPORT FROM MR. LENEHAN.
Government Observatory, Sydney, New South Wales,
H. C. Russell, Esq., 12 December, 1874.
Government Astronomer.
Sir,
I have the honor to report result of my observations of the transit
of Venus on the 9th instant.
The instrument used by me was an old telescope by Troughton & instrument.
Sims of London, with a focal length of 6 feet 9 inches — an 80-power eye-
piece, and neutral shade glasses of different densities — an aperture of 4f
inches, stopped down to 4 inches by a cap over object-glass ; fitted
on equatorial stand and iincler cover of a temporary observing dome.
At about llh. 45m. I took my station at the eye-piece and atten- Work-
tively watched for the first appearance of the planet, having everything in
my favour for a good result — definition of telescope, weather and clearness
of atmosphere, all that could be desired, with the scattered spots upon the
sun's disc showing sharp and clear.
The first indent on the sun's edge by the planet was observed at First contact.
llh. 55m. 36-34s., although I fancy from the contact then formed I could
have seen it 10 or 15 seconds earlier had I known the exact spot of
entrance.
The planet had crept on the sun's disc about one-fifth its diameter
at llh. 58m. 21'34s., definition clear and sharp.
At 12h. 1m. 31'34s. about one-fourth on, and at 12h. 5m. fancied I
saw the outer edge of planet, but was not perfectly clear on that point.
The sun's limb had bisected the disc of Venus at 12h. 7m. 8s., still Bisected,
clear and well defined ; at 12h. 12m. 30s. it looked as if the edge of planet
was losing its curvature, but later I found I was mistaken, as the cusps
reformed, giving the true curve to the planet.
About three-fourths of the planet on the sun at 12h. 15m. 54s., edge A.\'?lanct
= TiBible.
of planet off the sun discernible, but no drop formation.
At time of ingress there was an indistinct shading between the
supposed edge of planet and the sun, which for some ten or fifteen seconds
before the time I quote later, kept me in a state of uncertainty as to true
10 TRANSIT OF VENUS.
Shading. time of actual ingress. The shading did not break abruptly, but seemed to
melt away in such a manner as to leave a doubt in my mind of the exact
Band of ligLt. time the planet passed the edge of the sun, but I distinctly saw a clear
band of light at 12h. 24m. 48'34s. Then I left the telescope for the
photographic room, preparing the plates for exposure in large equatorial
until about ten minutes before first contact of egress, when I returned to
my telescope on the north side of the Observatory to observe the egress.
The planet stood out on the sun's disc with a clear and sharp outline,
with a luminous appearance or halo outside it about one-third diameter of
the planet (plate XVII), of a greenish yellow, with outer edge an orange
shade, as if the planet had an atmosphere, or perhaps caused intense
brilliancy on that part of the sun's face by rays being reflected. The
atmosphere was clear, and the following observations were made under very
favourable circumstances.
There was a similar indistinctness betwceen the time I mention as
" apparent contact" and " complete contact" as noted in the former portion
of this report at time of ingress.
Egress. The first apparent contact was at 3h. 54m. 21'61s., a little jumping
First contact. »(platc XVIIj fig_ 3), afterwards saw a band or faint and narrow streak of
light between limb of planet and sun which clearly showed the time given
was in error (plate XVII, fig. 3). I then waited until I was absolutely
certain contact was completed, which was at 3h. 54rn. 46'61s., I feel con-
fident that this time is from seven to ten seconds after true time ; thinking
the light might again show between made me wait till I was quite certain
before I noted the second time.
Cusps indis- At 3h. 56m. 26'61s. the points of the sun cusps appeared blunted as
if from vibration, and at 3h. 58m. 6'61s. this formation or appearance had
somewhat increased (this formation was like capillary attraction between
the planet's limb and the dark sky). The planet was about one-fourth its
diameter off at 4h. Om. ll'Gls.; at two minutes later the planet's edge off
Halo. sun was apparent. Half off at 4h. 9m. 1'Gls., the halo still showing
around that portion of the planet on sun's disc ; about three-fourths off, at
Spot of light. 4h.l6m. 21'61s. with the outer edge apparent, and noticed spot of light on
1Ct' preceding limb of planet, as shown at A (plate XVII, fig. 4) ; did not appear
to me as anything more than a spot.
The last and final contact at 4h. 23m. 49'61s., the edge of planet
being then lost in edge of sun.
» In phte XVII the diagrams should have been numbered 1, 2, 3, 4 from right to left.
TEANSIT OF VENUS. 11
These observations were made through a dark neutral shade eye-
piece, and were not at all trying to my sight.
Shortly after the finish of observations the atmosphere seemed to
become very smoky and thick, but altogether Sydney was favoured with
very fine weather.
I have the honor, &c.,
HENRY A. LENEHAN,
Computer.
REPORT FROM MR. SAVAGE.
II. C. Russell, Esq , B.A., Sydney Observatory,
Government Astronomer, — 21 December, 1874.
Sir,
I hereby give you a short report of what came under my notice
during the transit of Venus on December 9th, 1871.
The telescope allotted to me was a 10-inch reflector by Browning, instrument,
of London, with an unsilvered speculum, and focal length of 6 feet 2 inches',
with an eye-piece magnifying 200 diameters ; a dark glass slide was used
to protect the eye from the intense heat of the sun, the day being very hot.
Shortly before the time for first contact I was at the telescope, but the
instrument being a reflector and strange to me, caused me to lose the
observation before I could get the telescope to bear on that portion of the
sun's limb where first contact took place.
The next point for observing the planet was when it was bisected, Bisected.
the time of which I noted as 12h. Cm. 33'93s. and the apparent internal
contact at 12h. 22m. l'93s., the definition at this point being very bad
between the limbs of the sun and planet.
As the planet advanced on the sun's disc a little way a shading
connected the planet with the sun's edge, but that portion of it nearest Shading of
to the planet showed indications of fading away gradually, until at length CT
it disappeared altogether without any sudden break whatever, and at
12h. 23m. 43'93s. a streak of light became visible between the planet and
sun's limb.
12
TEANSIT OP YENUS.
Polar spot.
Egress.
For the same reason as above stated I did not observe the first
contact at egress ; the planet when I got it fairly in the field was about \ of
its diameter off the sun. The bisection of the planet took place by my
observation about 4h. 5m. 49'68s. I did not see any outline of the outer
edge of the planet during egress, but I did see a momentary flash of light
in the position shown in plate XI, but I did not record the time. The last
external contact of the planet with the sun's limb I recorded as being 4h.
19m. 32-68s.
During the ingress and egress the definition of both the sun and
planet was very fine. Through my not being able to get the first contact
at ingress and egress the clock motion was dispensed with, and I moved
the telescope gently by hand as it required. The interval between ingress
and egress I was engaged in equatorial tower, keeping time records of each
photograph taken.
EDWIN GEORGE SAVAGE,
Meteorological Assistant,
Government Observatory,
Sydney.
WOODFORD REPORTS.
REPOUT FROM THE SURVEYOR-GENERAL re TRANSIT OF VENUS OBSERVA-
TIONS AT WOOD FORD, ADDRESSED TO THE GOVERNMENT ASTRONOMER.
Surveyor General's Office, Sydney, 21 December, 1874.
Dear Sir,
I have to report the favourable observation of the transit of
Position of Venus, at the temporary Observatory at Woodf ord, on the Western Railway,
>rd' 54 miles west of Sydney, 2,200 feet above the sea, latitude 33° 43' 58-7",
long. lOh. 1m. 56'20s. (for details see Appendix 5), and to append the
reports of Messrs. Vessey, Hirst, and Dufaur.
TEANSIT OP VENUS. 13
The duties of each member of the party of observation were taken D
up as nearly as possible in accordance with your wishes ; and I much u y'
regret the breaking of the glasses dark of the 3-inch Cooke telescope, by
which we are almost deprived of the value of Mr. Dufaur's observations.
Leaving Sydney on Monday, the 23rd ultimo, I was employed until Preparation.
Thursday afternoon in marking out the position to be occupied by each
observatory, unpacking and attending to the instruments, which were
thoroughly wet by rain which fell at the time the packages were put down
by the train, and which continued the three following days ; little progress
could therefore be made in the erection of the piers, the earth being
saturated with wet, so I returned to Sydney, and revisited the camp on
the 30th ultimo, accompanied by Mr. Hirst, and was followed the next day
by Messrs. Vessey, Bischoff, and Dufaur. The day after we were fully
employed in setting up instruments, consisting of the photoheliograph by
Dallmeyer, the siderial clock by Cooke & Sons, a chronograph, the 4-|-
inch Schroder telescope, kindly lent by A. Fairfax, Esq., a 3-inch telescope
by Cooke, and a portable transit instrument — the two latter being supplied
by the Survey Department.
The place of observation was about 200 yards westerly from Mr. situation.
Fairfax's house (Woodford), and the same distance northerly from the
Western Railway and Telegraph line, and nearly upon the summit of the
main dividing ground between the waters of the river Cox on the south and
the river Grose on the north. So narrow was the ridge in the direction of
the meridian, that we could not get a tree or any object as a referring mark
without crossing the valleys, which would have made the mark most incon-
venient, and it therefore became necessary to erect a theodolite upon the
rock, within 70 yards of the transit instrument, to be used as a referring
mark, by observing one of its wires with the transit instrument.
Until the 5th the weather was most unfavourable for observations of Weather,
any kind, but opportunity was taken of every fine opening to adjust the
photoheliograph, which, being of peculiar construction, was not so easily instruments.
adjusted as an ordinary equatorial. During this time ample opportunity
was afforded of testing the value of the improvements made by yourself
upon this instrument since it was imported into this Colony, especially the
substitution of an eye-piece for adjusting it instead of the ground glass-
shade. With this we were able to get a fair image of a star in the same focus
as the image of the wires, so that the instrument with camera attached
became almost as easy to manage as an ordinary equatorial, and the adjust-
ments of both the stand and reference lines were made perfectly satisfactory.
14 TRANSIT OF VENUS.
The arrangement also by which the object-glass of the photohclio-
graph was made to pass through a sleeve of non-actinic calico attached to
the shutter opening in the roof converted the observatory into a photo-
graphic room, and gave us every facility for taking the pictures quickly ;
because it was not necessary to use a dark slide to transfer the plates to the
camera ; they were taken out of the bath and put at once into the frame
which had been fixed in the camera to receive them, and ensure an accurate
focal position for all the plates. We found the lever and spring attached
to the flashing shutter much more convenient to work than the cumbrous
arrangement for working the shutter with which the instrument arrived here.
o O
Telegraphic On the Gth instant we were, through the kind co-operation of the
tion. Superintendent of Telegraphs, in electric communication with Sydney
Observatory, a matter of considerable moment, as we were, through the
Difficulties unfavourable state of the weather, all behind with our transit observations.
owing to bad
weather. and telegraphic communication enabled us to compare our time with the
clock in the Sydney Observatory. The telegraph instrument was set up in
a tent close to both the clock and transit rooms. After transit observations
on two successive evenings for time and longitude, I found, on the 7th
instant, when preparing for observing sun's meridian passage, that the
sixth wire had broken and become entangled with two others. I restored
them to position and supplied the missing one, but only to be again dis-
appointed, wire No. 4 breaking before we had any further observation, so I
determined on sending the instrument to Sydney for new wires, and make
the observations for latitude and longitude at convenience.
Weather on The morning of the 9th was ushered in with a dry, hot, westerly
wind, which increased to almost a gale at 10 o'clock. Shortly after 10 AVC
received your latest time signals ; and after wishing success, and asking
further signals as soon after the transit as possible, we each took our
stations, from which time I have personally no knowledge of any occur-
rences beyond the interior of the photoheliograph and chronograph room,
Temperature, the temperature of which was noted half-hourly. The result thereof
appears as Appendix No. 3 to this report. My greatest anxiety was for the
Amiety for maintenance of as even a temperature for the clock as possible, and but for
tur" foTckick" the continual revolution of the fan ventilator and the constant application of
wet blankets, we should have found it difficult even to exist in the closed
room. The temperature, however remained as steady as could be expected
under the circumstances. Tor the observation of time of ingress and
egress and the phenomena observed with the 4f-inch telescope I refer you
TEANSIT OF VENUS. 15
to Mr. Surveyor Vesscy's report ; and from his skill and practice in delinea- Mr-
tion of form, and its relationships, I have great confidence in his observa-
tions, especially of the egress after he had time to realize the entire absence
of expected phenomena.
I have next to invite your attention to the somewhat conflicting Mr- Hirst>
report of Mr. Hirst, given as Appendix No. 2, who distinctly saw a "drop'' Blackdr°p-
whilst observing for position through the finder of the heliograph, and in
reply to my inquiry as to its appearance, said " more like a stalk." I
regret now that I did not leave my work to witness the appearance myself>
hut thinking that others would sec it, I did not wish a break in recording.
I cannot account for the appearance reported by him, unless it arose from
some optical delusion, resulting from the boiling appearance of the limbs
of both the sun and planet when seen through a telescope of small aperture
with an inferior lens. My experience of Mr. Hirst fully realized your
expectations of him as a gentleman of untiring zeal.
I have next to invite your attention to a short report from Mr. Mr. Fairfai.
Fairfax, to whose kindness and ready assistance we owe so much. Mr.
Fairfax, though not actually taking part in our work, was yet present
giving every assistance, and when the telescope was not otherwise in use
he took advantage of the interval to get a look at Venus. His report,
though short, is important, bearing as it does directly upon the character
of the ring of light seen round Venus. From his keen sight and long Halo
experience as an amateur observer I attach much weight to his report.
[Appendix 7.]
Before leaving the subject, I should like to say that, even if we have
not succeeded quite as well as we had hoped to do under more favourable
circumstances, still I shall always look back upon our expedition with great
pleasure. We agreed together well throughout, and can all bear testimony
to the kindness of Mr. Fairfax in placing his house and servants at our
disposal, and last, not least, the use of his excellent telescope.
During some of the intervals of weather favourable for observation clearness of
-r ,. ,, atmosphere.
1 saw some or the groups 01 stars in Argo in a degree of perfection rarely
to be hoped for in Sydney, fully bearing out the high estimate you place
on the Blue Mountains as a point of great advantage in observing celestial
phenomena. I remain, &c.,
P. F. ADAMS,
Surveyor-General,
N. S. Wales.
16 TRANSIT OP VENUS.
APPENDIX No. 1.
REPOKT of Observations made by L. A. Vessey during Transit of Venus,
9th December, 1874, at Woodford, Blue Mountains, N.S.W., trans.
mitted to the Surveyor General.
Instrument. ItfSTEUMENT, a 4f-inch. refractor by Schroder, stopped to 4* inches aperture, and equutorially
mounted in a canvas observatory with revolving dome.
Eye-piece diagonal, with one greenish neutral glass, and power 96.
Chronometer. Sidereal chronometer by Frodsham, repeatedly compared with sidereal clock ; times
reduced to Sydney mean time. For convenience of observation and for the purpose of
No shape. verifying apparent irregularities in the shape of Venus the diagonal eye-piece was used in
different directions during the transit. At commencement of ingress it was pointed north,
after ingress it was used for the most part pointing west, this being the position in which it
was screwed home.
Unsatis- The time observations at the internal contacts are very unsatisfactory. At ingress a
actory con" gust of wind causing the telescope to vibrate fully half the diameter of Venus prevented a
clear view of the phenomena, and the exhaustion caused by heavy night work in giving assist-
ance with the adjustments of the photoheliograph, brought about a certain amount of
nervousness in. the observer at the critical moments, which was not lessened by the totally
unexpected nature of the phenomena that occurred.
Clear idea of At egress the time observations were better, but the imperfect observation of ingress
did not give the observer a clear idea of the phenomena he might expect at egress, and he
was somewhat flurried by their gradual succession and the consequent impossibility of
determining the precise moments of their occurrence.
First contact. Indentation of planet first seen on disc of sun, but unfortunately no attempt was
made at the time to estimate the length of the notch. Time, llh. 55m. 14'96s.
Boiling. There was a good deal of boiling on the limb of the sun, but not quite so much on
Venus.
The planet appeared slightly flattened on that portion of the limb nearest the sun's
centre, and with a slight bulge near northern termination of limb. (Plate I, fig. 1.)
The eye-piece was now changed for one of power 195, with two dark glasses, but the
definition not proving so good the 96 was resumed, and the diagonal pointed west, — i.e., the
observer sat facing west.
Half-ingress. Estimated time of half-ingress, 12h. 7m. O'OOs. Previous to this a slight halo 3" or
4'' within the disc of the planet was seen extending about 60° in each side from the limb of
the sun, and resembling a gradually fading line of dots about 2" wide. (Plate I, fig. 2.)
There was no similar appearance on the limb of the sun, and the phenomenon remained
constant, although the position of observer's head and the direction of the diagonal were
repeatedly changed. The definition at this time was very good, the boiling practically nil, and
the sun's limb wonderfully sharp, with the very slightest glare, which was evidently merely
ocular.
TBANSIT OF VENUS. 17
Tho following limb of Venus distinctly defined by a faint line of light, which was Ri»g of light,
rather brighter on northern side. (Plate I.) (Fig. 3 at 12h. 15m. 30'OOs.*) This line of light
very distinct. Making Venus a complete circle.
Definition good, very little boiling.
Eing of light increasing in beauty, silvery ; decidedly brighter on north side of middle Inequality in
sketch, perhaps V in thickness. (Fig. 4, Plate I, 12h. 19m. 30s.)
Apparent internal contact estimated too soon,— 12h. 23m. 27'12s.
Time of ingress taken, — 12h. 23m. 47'07s. contact.
Ingress certainly complete,— about 12h. 24m. Os. Keal internal
contact.
The original note here is — " the telescope was much shaken by wind at 12h. 23m. and
afterwards, and the ring of light around Venus cut through what would otherwise, I think,
have been a drop, lasting 40 seconds, if not a whole minute." That this was a mistaken
impression, and the natural result of the motion of the telescope, the notes at egress will
clearly show. (Plate II.)
Definition magnificent at 12h. 30m. 30'4s. ; atmospheric ring on disc of planet, corre-
sponding to the halo noticed before (sec fig. 2, plate I), but broader and gradually shading off Globular
towards the centre, to be traced all round, giving Venus an appearance of relief like an oblate Of planet,
spheroid, or rather a flattened dome standing away from the sun, the radius of the flattened
part being about half that of the planet. (Plate VII, fig. 1.)
The observer then entered the photoheliograph room to assist in taking the large
photographs, and had only an occasional hurried glance through the telescope till near the
time of egress.
Definition very good, 3h. 46m.
The note made at ingress shows that the observer was, by his imperfect view of that Egress,
phenomenon, fully prepared to sec a drop of perhaps 2" in length divided by the ring of light
around the planet, but the appearances that did present themselves at egress were very
different, and to the observer certainly gradual, without the slightest suspicion of a sudden
change or break in the light between the limbs of the sun and planet ; the sun's light
diminished till nothing but the silvery ring of light around the planet was left, and this ring
was carried out on the sky by the slow motion of the planet.
About this time, 3h. 54m. 25'47s. (see plate IV), the light between the limbs of the Apparent
sun and the planet became so thin that in observer's estimation all direct sunlight was cut |"c*r™ eg°e88.
off and nothing but the ring of light arouud the planet remained ; or in other words, the
narrowing of the line of sunlight between the sky and planet then seemed to cease.
At 3h. 54m. 37'50s. the cusps of the sun's limb were distinctly separated but connected
by the fine ring of light around the planet. This ring was rather whiter than the sunlight,
and the cusps at their extremities appeared very slightly thicker than the ring.
This thickening was only just perceptible, and might possibly have been caused by
fatigue of the eye, requiring relief by a slight change of focus, or even by an unconscious
mental influence, leading (he observer to see what he was expecting and wishing to see.
(Plate V.)
At 3h. 54m. 48'41s. the circles of the sun and planet tangential, and the ring of light
about its own thickness outside the limb of the sun. (Plate VI.). (See next pa^e, halo Intcrnal con"
tact,
estimate as 1" in diameter.)
* The time on Fig. 3, Plate 1, is in error, it should be Oh. luui. 30s.
C
18 TBANS1T OP VENUS.
Apparent in- The ring now distinctly showing as an arch outside the sun's limb, 31i. 55m. 3'37s.
ternnl contact
decidedlypast.
Venus not cir- At 4h. 2m. 80s., Venus not quite circular, slight flattening on the eastern side of the
King planet as shown in sketch, ring of light brighter near limb of sun at eastern side, or at N.N.E.
part of planet appearing as a sharply defined line without haze or irradiation, and less than
1" in thickness. (Plate VII, fig. 2.)
Planet copper- At 4h. 9m. Os., disc of Venus still continuous, undoubtedly a globe, and appearing
slightly reddish or copper-coloured like the moon in an eclipse ; the sky adjoining intensely
black, with the suspicion of a greenish tinge contrasting with the colour on the planet.
(Plate VII, fig. 3.)
Eepeated comparisons were made between planet and sky to verify this.
Half egress. At 4h. 7m. 44'37s., probably estimated too early and a difficult observation to make, as a
temporary shift of wind brought the heated air from the roof of the photoheliograph buildinrr
across the Bun, causing a sharp jagged boil.
At 4h. 17m. Os., Venus not quite circular, the curve of planet's limb slightly flattened
on eastern side, with a slight bulge on western side. (Plato VII, fig. 4.)
Final contact. At "ln- 24m' 3'40s-. last contact at egress. This observation appeared to be correct to a
small fraction of a second. The indentation on sun's limb gradually contracted in width till
about 12h. 23m. 51s., it then seemed to contract longitudinally till it became a small notch
like a boiling indentation. This was seen steadily diminishing till it suddenly flashed out and
the limb of the sun became perfect at 4h. 24m. 3'40s.
Definition very good, and boiling of sun's edge scarcely perceptible.
L. ABINGTON VESSET,
Licensed Surveyor, New South Wales.
APPENDIX to Mr. Vessey's Eeport, with complete drawings of phenomena observed, trans-
mitted to the Government Astronomer, by L. A. Vesscy, Licensed Surveyor.
Scale of THE thirteen diagrams which accompany this Appendix have been drawn, the smaller ones on
diagrams. a scale of 40" = 1 inch, and the larger 40" = 3 inches, and the phases of the planet and points
of the compass have been laid down with all needful accuracy. The drawings have been
executed after much consideration, and represent to the best of my ability the appearances
presented in the telescope ; the smaller ones should be viewed at a distance of 5 feet, the
larger at about 10 or 12 feet.
Drop phrase- In my report I unconsciously adopted the phraseology I had become accustomed to
ology. when using the artificial transit ; the drawings will prevent any ambiguity that might arise
from this cause at the critical times of internal contacts, and will make the report more
precise throughout.
Through pressure of professional duties and the large call upon my leisure, made by
the necessary preparations, I did not read up accounts of past transits carefully, except as
referring to the " black drop," but gave my entire attention to acquiring accuracy in taking
time and the estimation of tangential contact with the artificial transit. I did not expect
there would bo any physical appearances to record except at the critical moments, and I
determined then to make sure of my times in the first place, and neglect (if need be) anything
else that promised to interfere with that object.
Free from I therefore went to the telescope perfectly free from mental bias, and with the
bias. exception of the slight eccantricity shown in plate I, fig. 1, watched the planet creep, black
and uninteresting as the sky itself, upon the sun's limb.
TEANSIT OF VENUS. 19
At the time when my attention was specially drawn to the cusps of the planet in the
endeavour to estimate the time of half ingress I saw the halo. (Plate I, fig. 2.) The idea
of an atmosphere instantly presented itself, but was succeeded as quickly by the thought that pianet
the halo was only an optical illusion, and I waited impatiently till the half ingress was past
and I had leisure to test this. I then revolved the eye-piece 90°, changed the position of my
head, and carefully compared the limbs of the planet with the adjoining limbs of the sun,
and was at length satisfied that the halo was a reality and not telescopic ; the sun's limb was
sharply defined with only a suspicion of a glare as indicated in the drawing, in no way
resembling the halo on the planet. The phenomenon remained constant, and I watched it
steadily for some minutes, in fact to the best of my recollection until I caught sight of the jj. j on j. b
ring of light shown in fig. 3. The beautiful pearly yet sparkling light of this ring would of ,,ianet_
alone have been sufficient to fix my attention, even if its increasing brilliancy had not made
plain that the observation of the expected black drop would be rendered very difficult when
complicated by the presence of such a bright edge to the planet. Figure 3, plate I shows the
northern segment of the ring brighter than the rest ; fig. 4, plate I the north part decidedly
brighter aud corresponding exactly to the bright part in plate VII, fig. 2.
The halo was not looked for, and was not seen till the time (plate I, diagram 3) P°lar Part of
when it appeared under a somewhat different form and was continuous round the planet ; at rmR'
egress it was not specially noticed. My note on (fig. 3, plate VII) "globular" seems to
point to something of the kind in addition to the copper color, but not being certain of this I
have not shown it in the drawing.
Plate II illustrates the phase of ingress which I endeavoured to catch as the " apparent" Apparent
or tangential contact of the limbs of planet and sun (in the drawing they slightly overlap to contact,
give the desired effect). For a minute succeeding this a most untimely gust of wind kept the
telescope vibrating, and plate III is only given as a representation of what I thought I saw
during this time. There was much dimness and uncertainty about the cusps, whether from
the motion of the telescope or otherwise, and this cleared off and the telescope became steady
between the time given against " ingress certainly complete." There was certainly no blunting
of the cusps of sunlight nor indication of the formation of a "drop" up to Oh. 23m. 47s., the
time of plate II.
At egress I watched the planet creep up to the sun's edge ; there was not the slightest Egress. No
uncertainty or cloudiness between their limbs, and I waited patiently till I judged the sun's unsteadiness,
limb could not longer remain unbroken, remembering the thickness of tho ring at ingress,
before I noted the time of what I considered " real " contact under the black drop nomenclature
(plate IV.)
Twelve seconds later gave me the appearance shown in plate V ; this in the drawing is Diagram,
probably exaggerated, and it is the only reliable indication of a drop that presented itself; Internal
eleven seconds afterwards I judged the tangential or true internal contact took place (plate VI) . c°ntact.
The breadth of the ring of light is here' an important consideration ; during the transit
I did not attempt to estimate it, but afterwards set it down as never much exceeding the i ihyth ^r® °*
part of tho planet's diameter, or as 1" in thickness at the greatest. That this was an over-
estimate will appear from the drawings and from the times recorded at egress. Even on the
comparatively dull white of the paper a breadth of y gives the full effect required, and tho
interval in time of 23 seconds between plates IV and VI corresponding to a motion of t in the
planet is a strong confirmation of the breadth given in the drawings, especially when from the
nature of the phenomena the first time would probably be taken a trifle early and the second
a little late, or when the planet was really slightly overlapping the sun's edge (in the drawing
it overlaps considerably to give the desired effect).
Thus plate VI is equivalent to the estimation of the thickness of a line %'' wide with
magnifying power 96. The exact measurement is of course impossible, but that some i';lir Measureof '''•
approximation may be made will be evident if it is considered that a lino 4 l^th inch thick
viewed at a distance of 30 inches subtends tho required angle of \" under such magnifying
power, and a bend in the line corresponding to " the ring of light about its own thickness
outside limb of sun" would be easily seen, especially to an eye practised almost daily in the
reading of verniers.
Plate VII, fig. 2, shows the ring of light with a bright part on the N.N.E. side corre-
sponding to plate I, fig. 3, also a decided irregularity in the shape of the planet which fig. 4,
plate VII, shows to have remained unchanged for a quarter of an hour ; the bulge on the
south-west side does not seem to agree exactly with that shown in fig. 1 plate I, but there is
sufficient approximation to make me await with interest the reports of other observers.
20
Contrast of
colour.
TEANSIT OF VENUS.
Fig. 3 plate VII is an attempt to show the contrast of colour between the disc of the
planet and the sky ; this colouring claimed my attention for the time, and the planet is shown as
circular and the ring as uniform iu brightness, simply because I have no special note about
either ; and my attention being otherwise engaged, recollection will not serve me further than
that the ring was there and was continuous, helping me in contrasting the planet with the sky
L. A. VESSET.
APPENDIX No. 2.
MR. HIRST'S REPORT.
Temporary Observatory, Woodford, 9 December, 187-1.
I HAVE to report on matters especially under my charge and connected with the transit of
Venus which has taken place to-day.
Instrument. The instrument with which I was particularly concerned was a photoheliograph by
Dalmeyer, similar to those supplied by him to all the English parties, and provided with a
Jansen's apparatus for obtaining a number of photographs during ingress and egress. Attached
to the tube of the heliograph was a finder, consisting of a single lens li in. aperture and about
4 feet focal length. This was originally arranged by the maker so as to throw the sun's
image oil to a piece of parchment fixed at its focus ; but in order to adapt it to circumstances
which required that one end of the photoheliograph should be in the photographer's dark
room, the lens was inserted in the end of a brass tube, and an eye-piece provided in the shape
of a Huyghenian combination, giving a power of about 50 diameters. The chromatic and
spherical aberration of the single lens was in part compensated by its extreme focal length
so that fair definition could be obtained of the edge of the sun and the existence of even
minute solar spots made plainly visible.
To diminish the light in the finder I used a thick piece of orange-coloured glass, which
gave an agreeable colour to the sun ; this was placed outside the eye-lens of the eye-piece.
Ingress. ^g ^e ^jme fQf grg^. cxtemal contact drew near, I attentively watched the portion of
the sun's limb where I expected Venus to appear, and within 20 seconds after first contact
was reported by an observer at the 4-J-in. equatorial, I picked up the planet in the finder.
Jansen plates. j then commenced taking as many of the circular Jansen plates as possible, referring
to the finder between each plate to satisfy myself that the heliograph had not shifted. Venus
continued to encroach upon the solar disc, preserving at the same time a regular circular
form ; definition at this time excellent.
Black drop. I had prepared and placed a plate in the Jansen eye-piece, when, on taking my usual
glance at the finder, I observed the disc of Venus appearing, as it were, rather more than one-
third her own diameter within the sun, and connected with the limb by a narrow line intensely
black with an ill-defined edge (see plate XIV), which represents the appearance as faithfully
as I can recollect ; this was about five seconds before No. 5 Jansen plate was begun. I had not
time for more than a glance, for I wished to procure a photograph of what I supposed to be
the black drop so universally observed by astronomers more than a century ago at the last
transit. On getting the plate through, however, it showed nothing of what I had so distinctly
observed a few seconds before. (See plate XIV.)
TEANSIT OF VENUS. 21
deferring to the finder, Venus appeared well inside the sun, but apparently nearer the
limb than she seemed before the drop was gone. I thought at the time that it might have
broken before the exposure of the plate, and I determined to keep a sharp look-out for its
formation at egress. Soon afterwards Mr. Vessey came in, and reported that the 4j-in. had
shown no drop at all.
Towards egress I referred constantly to the finder, that I might be ready with a plate Egress,
directly the drop became visible. When Jansen plate No. 9 was in its place, and upon adjusting
with the finder, I observed no black drop, the planet appearing so far within the sun's disc
that I did not think it necessary to hurry in order to catch the drop, and exposed the No. 9 .
plate, meaning to got another in in time. After taking out the plate, which probably occupied
20 seconds, I went to the finder, and, to my astonishment, saw that the drop had formed, Black drop,
appearing about as long as one-third the diameter of the planet. I hurried on the next plate
as much as possible, but a delay unfortunately of a couple of minutes occurred before it was
ready ; on development it showed Venus as a perfectly circular disc touching the sun's limb.
I regret exceedingly that my eye was not at the finder during the precise moment of
the formation of the drop, but my duties at the Jansen eye-piece prevented me from staying
there more than a few seconds at a time.
Eeferring to what I saw through the finder, I am convinced that my observations, short Sure of
though they were, have not deceived me. I was thoroughly prepared and on the look-out for Plleuomena-
the phenomenon at egress, and I have not the slightest doubt that any one using similar optical
means would have seen what I did.
I have forgotten to mention that Mr. Vessey at the 4£-in. reported no drop at egress.
GEO. D. HIEST.
P.S. — About mid-transit during a pause in taking photographs, I examined Venus with Halo on
Mr. Fairfax's 4:J equatorial. The planet appeared intensely black, and perfectly circular, but *cnus-
it was surrounded by a narrow fringe of dull red light. I was only able to watch it for a
minute, when other duties demanded my attention. I used a neutral tint glass, so that the
red colour cannot be attributed to it. (See plate XV.)
(Note by H.C.E.).— The exposure of plate No. 9 was begun at 3h. 51m. 42'42s. and
was finished at 3h. 52m. 31'39s. At 3h. 53m. 3s. Mr. Hirst looked in the finder and saw the
black drop. Mr. Vessey saw the actual contact of limbs at 3h. 54m. 48'41s. or 1m. 45'41s.
after Mr. Hirst saw the black drop. So that the inferior telescope produced the black drop
certainly 1m. 45'41s. and perhaps more before actual contact took place.
APPENDIX No. 3.
MB. DuFAiiii's REPORT.
Temporary Observatory, Woodford, Wednesday, 9 December, 1874.
INSTRUMENT used, Cookc telescope, equatorially mounted, but without rack adjustment for Instrument,
focus or screw motion, aperture 3 inches, power Go. Previously to commencement of transit,
the only two coloured glasses having been fractured by heat of sun's rays, the field lens was
22
TRANSIT OF VENUS.
Focus.
Lost contact,
No distortion,
Perfect '
definition.
Egregs.
Lens broken.
No black
drop.
smoked, and almost immediately succumbed to the same influence, being starred in all
directions. Under these circumstances, added to the difficulty of adjustment to focus, and in
retaining the sun's limb in the small portion of the field of view remaining available, all hope
of satisfactory time observations were destroyed. The last contact at ingress and first at
egress were observed. At ingress the whole body of the planet was discernible when only
about two-thirds of it had entered on the sun's disc. I estimated an interval of about 4
seconds from the time when I judged the planet to be wholly on the sun's disc and the time
when the first light was apparent between their edges : though there was but little boiling of
the sun's limb, this first appearance of light was by no means instantaneous, no black drop was
formed, and under the circumstances in which I was placed, little (if any) distortion of the
planet's following limb was observable. A gust of wind which came up at that time, together
with the noise caused by the blower attached to the adjacent dark house, rendered my
chronometer, which could not be placed within the range of my vision, inaudible for a con-
siderable space of time, and I could place no reliance on my estimate of the time of completed
ingress.
During the time that the planet was passing over the sun's disc, between that of com-
pleted ingress and of the first contact at egress, I had full opportunities of watching its pro-
gress through the 4:] -inch telescope ; the definition was very perfect at times, and I constantly
focused the glass by the groups of sun-spots (of which I could detect about twenty-four) and
not by the planet's disc. Thus focused, that disc appeared to me perfectly defined, at times when.
scarcely any boiling was observable, and was as sharp as it would be possible to illustrate it
on paper ; I could detect no inequalities in its edges — it appeared to me perfectly black.
Returning to the small telescope to watch the egress I found the lens still further
starred, so as to render it extremely difficult to follow the planet at all satisfactorily, but I
again estimated a lapse of about 40 seconds between first real and apparent contact. I again
failed to observe any black drop, but the vanishing of the thread of light previous to apparent
contact, so far from being instantaneous, was so gradual and ill-defined, owing to the state of
my instrument and my inability to adjust the focus satisfactorily without rackwork, as my
eye became weary and required such readjustment, that I am afraid I must again consider the
time taken, Sydney mean time, 3h. 55m. 25.50s., to be of little value as an observation.
ECCLESTON DuFAUR.
Observations of Weather previous to and during Transit of Venus.
Temporary Observatory, Woodford, Blue Mountains, N.S.W.
Wednesday, 9th December, 1874.
10.30 a.m. — Sky perfectly cloudless. Light westerly wind.
11.30 a.m. — Light clouds forming.
O.Gi p.m.— Passing clouds crossing sun's disc.
0.7 „ — Sun's disc obscured for about 30 seconds.
0.9 „ — Thin clouds passing sun's disc.
1.0 „ — Passing clouds. Sun obscured for about 5 minutes.
Wind N.W. Almost calm at intervals.
1.7 „ — Large cloud passing over sun.
1.10 () — Clear. Thunderclouds rising in the west
TEANSIT OF VENUS.
23
1'23 p.m. — Passing clouds.
1'25 „ — Sun's disc obscured for 10 minutes.
Wind westerly — force about 3 with puffs.
2"1G „ — Clear. Thunderclouds to westward.
2'36 „ — Passing clouds.
2V10 ,, — No material obscuration during the remainder of the transit — at its close a
bank of clouds rising to south of west to within about 5° of the sun's position.
While the sun was unobsctired the planet's disc was clearly visible through a simple
smoked glass, up to the time when the egress was fully half completed.
Appended are hourly barometric and thermometric observations taken at Mr. Fairfax's
house, W oodford.
ECCLESTON DuFATJE.
Woodford, 9 December, 1874.
Barometer and Temperature.
Hour.
Barometer.
Temp.
Hour.
liarometer.
Temp.
6 a.m.
27-88
79-0
1 p.m.
27-85
90-0
7
27-88
81-2
2
27-83
90-0
8
27-88
83-2
3
27-80
91-0
9
27-89
85-0
4
. 27-78
91-0
10
27-88
862
5
27-77
88-8
11
27-88
87-5
6
27-77
86-0
12
27-87
88-8
APPENDIX No. 4.
TEMPEHATURE in Clock Eoom at the Woodford Observatory, during the observation of the
Transit of Venus, 1874.
Mean Time.
Temperature.
Remarks.
h. m.
0
8 0 a.m.
SO
9 0
88
9 30
92
10 0
92
10 30
91
11 0
92-5
Wet blankets applied to oulsidc of observatory.
11 30
92
12 0 noon
| No observa-
(_ tion taken.
1 0
92
1 30
93
2 0
93
- Wot blankets and ventilator used almost continuously.
2 30
94
3 0
94-2
!! 30
943
4 0
94
4 30
93-8
J
5 0
95
5 30
95-9
24 TRANSIT OP VENUS.
APPENDIX No. 5.
KESULTS of Observations for Longitude of Woodford : —
Difference
m. s.
December 21, 1874 ... y- Ceti 25479
aCeti 2 54-79
S Arietis 2 54'41
B.A.C. 1125 2 54-65
B.A.C. 1201 2 54-G9
/Eridani 2 54'79
o1 Eridani 2 54'58
e Tauri 2 54'52
aTauri 2 54'50
t Aurigae ... ... ... 2 54'41
Adopted longitude of Woodford west of Sydney... 2 54'G1
h. m. e.
Longitude of Sydney ... 10 4 50'Sl
0 2 54-61
Adopted mean longitude ... 10 1 56'20 of Woodford.
• ^_^_
EESULTS of Observations for Latitude of Woodford : —
o / //
December 27, 1874 ... B.A.C. 1150 .'.. ... 33 43 58'8
„ „ ... „ 2066 33 43 55'9
28, „ ... „ 1433 33 43 62'6
2066 33 43 57'6
Adopted mean latitude of Woodford 33 43 58'7
The longitude was determined by the transits of stars over the Sydney and Woodford
transits, the times being recorded on the Sydney chronograph.
The latitude was determined by placing the transit instrument in the prime vertical.
APPENDIX No. 7.
MR. FAIRFAX'S REPORT.
Woodford, 10 December, 1874.
Halo. DuniNG the time when the disc of Venus was slowly creeping on to the sun, I had
the opportunity of using my own glass (4J-in. equatorial) for a few moments. Venus was at
the time about two-thirds on the sun and appeared to me perfectly black, and all that part
which was seen with the sun as a background seemed to be as sharply defined as possible
without any haziness, but with the part off the sun it was different ; that was marked by a
most brilliant line, which was very narrow, and yet seemed to me like my drawing, plate XXIX,
which represents the general appearance, but I would not for one moment say that the
drawing is correct to scale ; in fact the halo was so narrow that I could not make a drawing
Colours. like it. Still I distinctly saw in that very narrow halo such forms and colours as I have
represented. It appeared as if Venus were surrounded with white and red flames mixed and
so close together that they formed a continuous ring which was probably less than -SV of the
diameter of Venus across.
A. FAIRFAX.
TEANSIT OF VENUS. 25
CAPT. -IIIXSON'S KEP01IT.
Goulburn, 10 December, 1874.
THE extraordinary power of the sun and its vertical position during the Powerof 8un-
period of ingress interfered materially with my observations. The weather
was comparatively mild previous to the 7th of the month, but on that day Temperature,
the maximum thermometer reached 102° in the shade, the wind being from
the westward and the atmosphere slightly disturbed by electric storms. A
small quantity of rain fell, but not sufficient to make any appreciable show
in the rain-gauge. On the following day, the 8th, the day previous to the
transit, the weather was of the same character, the maximum thermometer
registering 103° in the shade.
The 9th, the day of the transit, set in with the wind from the west- Weather of
ward, light in the morning, with occasionally drifting clouds ; the wind
increased to a force of about 6 in the Beaufort tables by 2 p.m. ; at this strong wind.
time about half of the sky clouded, the clouds occasionally but not seriously Clouds.
interfering with the observations. The thermometer at noon stood at Temperature.
101° ; at 1 p.m. it was 102°, and at 2 o'clock it was 104° and it remained
at this point up to 5 o'clock. The thermometer in the sun was not
regularly recorded, but at noon I am informed it was observed to be 130°.
The barometer was 27'82 inches at noon, 27'79 inches at 2 p.m., and Barometer.
27'73 inches at 5 p.m.
The heat was so great in the observatory for photographic work, Qre hc
notwithstanding that Mr. Russell had fitted a ventilating fan to it, that ventilator.
both I and Professor Livcrsidge remained in the sun uncovered some
seconds after coming out without being conscious of the danger we were
incurring until our attention was called to the fact of our being bare-
headed by a person in attendance.
I used a 6-inch equatorial telescope with a magnifying power of instrument
130 diameters. A shaded glass had been broken by the power of the sun
the day previous, and therefore I was careful to focus the instrument in
such a manner as to expose my shades to a gradual heat. Notwithstanding
this care but a short time elapsed before the glass in front of the lens
became fractured and it had to be removed. This was replaced by a smoked Olas3 broken.
glass, but soon the smoke evaporated and the glass became so cracked as to
26 TRANSIT OP VENUS.
be altogether useless. I next, with the assistance of Mr. Tornaghi, tried a
Coloured smoked glass over the object-glass of the telescope, but now the coloured
shades in my movable eye-piece both crave way, so that I was reduced to
holding in my hand the shaded glasses which Captain Onslow permitted me
to take out of his sextant. These became so heated as to be difficult to
hold ; this, coupled with the uncomfortable position I had to assume,
induced me to take Mr. Tornaghi's suggestion and attach the camera to
Contact. the telescope, and watch the image on the ground glass. In this way I
first observed the planet on the sun's disc at about 12h. 2m. 41 -06s. The
planet as I had the opportunity of observing it through the telescope
appeared to work its way on to the sun's disc without becoming disturbed
or to assume the shapes which we had been led to expect. The edges of
each object were well denned, the planet appearing quite dark and globular.
ingress. First internal contact was clearly noted to break by Mr. Tornaghi
observing the light of the cusps forcing its way from cither side between
the planet and the sun at 12h. 25m. 50'27s.
Photographs. Photographic work was commenced after first internal contact had
taken place.
Egress. My observations of egress were taken by holding a shaded glass to
protect my eyes, all the coloured glasses of the telescope having become
fractured as before described ; but this became an easy task now, as the
position of the sun was much more favom*able for observations than it was
at ingress, and it had moreover lost much of its power.
At 3h. 46m. 4'3Ss. the planet appeared a dark beautifully defined
globe, the sun's edge being also sharply defined.
I judged that contact took place at 3h. 54m. 28-01s. Previous to
this there was a portion of light visible between the planet and the sun.
•Bisected. At 4h. 10m. 0-45s. the planet appeared to be bisected by the edge
of the sun, both objects being clearly and sharply defined. The portion of
the planet off the sun was invisible to me.
Several clouds passed over at about this stage of the phenomenon.
Last contact. At 4h. 23m. 34'24s. I recorded last external contact, after which
the planet disappeared altogether. I observed a portion of the planet
illuminated, as I thought, at one time, but I do not consider my observations
in this respect of any value, as my shaded glasses were held in my hand and
occasionally spoiled the focus.
TRANSIT OP VENUS. 27
The day after the transit was not nearly so hot, and the day after
that the weather became quite temperate, and cold towards evening.
Appended will be found Reports from
Capt. A. Onslow,
Professor Liversidge,
Mr. A. Tornaghi.
THE instrument at my command for determining the latitude and longitude of the station was Altazimuth.
an altazimuth. Telescope 1-J-iu. aperture and focal length 19-in. vertical circle 15 inches
provided with two micrometer microscopes reading to 1".
As soon as this instrument was placed in the meridian the azimuth circle was clamped Longitude
and the observations made as with a transit circle. For the determination of the difference of "
longitude, selected stars were observed in transit over the meridian of Sydney. I then
observed them in transit over my instrument, and by means of a contact key sent the time of
transit over each of the seven wires to the chronograph in Sydney Observatory ; the difference
between the transit at Sydney and G-oulbum was thus measured by the standard clock, each
star afforded an independent determination of the difference in longitude, and it is satisfactory
to find such a small range in the differences, when the size of my instrument is considered.
I nsed the same stars together with a few others to determine the latitude, the observa-
tions being made in the same way as with a transit circle. The differences are not so small as
1 should have liked to see them, but no doubt the extreme heat of the weather gave rise to the
difficulty experienced in bisecting them.
The observing tents were placed in the middle of the Market Square, Goulburn, and
the brick pier on which the transit instrument was placed was left standing when we left.
The height of the observatory above mean sea level was 2,129 feet.
BESTJLTS of Observations for Longitude of Goulburn : —
Difference,
m. s.
December llth, 187-1... S Arietis 6 0'32
17 Tauri ... ... 6 0'25
No name 5 59'90
< Tauri ... 5 59'98
a Tauri 6 0'34
aTri. Aust 6 013
t Auriga? ... ... ... 6 0'27
t Leporis ... ... ... 6 0'04
/i Orionis 6 0'02
6 014
h. in. s.
Sydney longitude 10 4 50' 81
Difference of longitude 6 014
Adopted mean longitude ... 9 58 50'67
28 TRANSIT OF VENUS.
RESULTS OF OBSERVATIONS FOR LATITUDE OF OBSERVATORY.
December llth, 1874... 6 Ceti 34 44 43'70
77 Piscium 34 45 4'60
a Eridani 34 44 41'50
a Arietis 34 45 24'30
T-Ceti 31 45 9'80
8 Arietis 34 45 52'90
77Tauri... 34 45 45'20
o1 Eridani 34 45 21'10
tTauri 34 45 36'90
aTauri 34 45 0'20
i Aurigse 31 41 38'50
£ Leporis 34 44 56'80
/3 Orionis " Rigel" ... 31 45 29'30
Adopted mean latitude ... ... 34 45 12'G8
PEANCIS IIIXSON,
Capt., It.N.
CAPT. ONSLOW'S REPORT.
Ingress.
Telescope used 3-J-iu. equatorially mounted refractor.
TUB time of the planet's first apparent contact not recorded, as the planet was not seen till it
was well on the disc of the sun.
At 12h. 10m. 14'24s. half the sphere of the planet apparently on.
At 12h. 13m. 54'25s. the planet somewhat resembled the letter D or the top of a thumb
projecting over the sun's surface.
At 12h. IGin. 28'26s. a bright light was seen at the left point of intersection of the
two circles (fig. 1, plate XVI.), and in a few seconds a similar light at the right point (fig. 2) ;
time 12h. 16m. 34'2Gs.
At 12h. 19m. 29'28s. an apparent circle formed by planet, 12h. 21m. 29'28s. Venus
apparently just touching inner edge of sun.
At 12h. 23m. 29'28s. the internal contact appeared complete, but at this moment the
objects got out of my field of vision, and when again sighted 12h. 25m. 29'2Ss. the planet was
well inside the sun's limb.
Egress.
Observed by Mr. Tornaghi, time recorded by me :—
At 3h. 53m. 47'78s. the light between the interual edge of the sun and external edge of
the planet was a little dim though the circles were quite distinct.
3h. 54m. 25'79s. time of contact.
3h. 58m. 44'80s. about i off.
4h. 3m. 14'82s. the upper intersection to the right a little flattened.
Planet about half on 4h. 8m. 59'SOs.
about one fourth on 4 18 22'83
disappearance ... 4 23 27'84
A. ONSLOW.
TEANSIT OP VENUS. 29
PROFESSOR LIVERSIDGE'S REPORT.
Goulburn, 9 December, 1874.
Temperature ill shade, 104 '4.
THE instrument used was a 3-i-inch equatorial telescope, and the power employed was Instrument.
150 diameters. A red dark glass was screwed on over the eye-piece in the ordinary way ; the
neutral tint and blue dark glasses attached to a slide were found to be less convenient for use
although their lights were softer and less trying than the red.
The telescope was placed upon the brick pier built for the transit instrument ; this
pier was about 2 feet square, and rose some 22 inches out of the ground ; and the only
position which was permitted mo during the ingress was a reclining one, with my feet
to the east and my head to the west. I may mention that it was an uncomfortable and
unsteady one, and prevented me from taking such full notes at the time as I had wished.
The first stages of the ingress were not observed, so I accordingly waited until I judged
the planet was half on before recording any observations ; this took place at 12h. 7m
0'64s. ; the planet was apparently half on or bisected.
Ingress.
At 12h. 20ra. 5' Its. I was inclined to think that there was "apparent internal contact," internal
as seen in the artificial transit. contact.
At 12h. 21m. 4'14s. I again judged that there was " apparent internal contact,'*
and considered that my estimation of it at 12h. 20m. 5'14s. was made too soon
At 12h. 22m. 5'Gls. the circle of Venus appeared to be complete, and apparently Complete
just touching the sun's limb, i.e. " internal contact" really took place.
At 12h. 25m. 38'15s. the disc of Venus was clear of the sun's limb, and appeared
to be about J of the planet's diameter within it.
During the interval between the times 12h. 22m. 5'64s. and 12h. 25m. 38'15s. a faint Haziness,
hazy grey filament like a streak of smoke was momentarily observed between the edge
of the planet and the sun ; it was very obscure and ill-defined.
I unfortunately failed to note the exact time at which the cloudiness was present
between the two limbs, for while trying to get it more in focus and more sharply defined it
vanished. There did not appear to be any sudden break in it, but it faded away quite
'in perceptibly.
K"o traces of the " black drop" were seen, unless the above be considered such.
The absence of the black drop and the unexpected manner in which the planet made its
ingress, unaccompanied by the distortions and other peculiarities previously predicted, rather
upset my expectations, and tend to make my observations of this portion of the transit less
comprehensive and detailed than they might otherwise have been.
Egress.
At 31i. 39m. 4()'31s. the planet was about one-third its diameter from the sun's Spheroidal,
upper left-hand limb ; it then appeared spheroidal, and not as a disc merely ; it appeared
illuminated on the inner side in the direction of the sun's diameter, and this illumination
30
TRANSIT OP VENUS.
shaded off on each side of the planet, but at the portion nearest to the sun's limb it appeared
quite black and opaque (Plate XXII, figs. 1, 2, 3).
Globular. This globular appearance was retained until the planet had passed off the sun's limb
to the extent of about J of its diameter.
Haziness. At 3h. 4Gm. 40'31s. I fancied I could see a slight haziness between the planet
and the solar limb. I do not attach any importance or value to this observation, as the
haziness was exceedingly ill-defined.
Contact. At 3h. 54m. 57 3ls. contact between the two limbs took place.
Processes. At 4h. Om. 2'3ls. the planet was just beginning to pass oft" the sun's limb, and
it looked somewhat as if it were pushing that portion of the sun's limb before it, for the solar
limb appeared to be raised up into two processes, one on each side. (Figs. 5 and 0, a and I.)
At the time I thought it might perhaps be due to an atmosphere surrounding Veiuifj
or to an optical illusion ; but since I have heard that other observers saw the illumined edge
of Venus beyond and outside of the sun, I am inclined to think it was that which I saw. I,
however, did not see a segment of a circle beyond the sun, but merely two portions or cusps
brightly illuminated, but not as bright as the sun.
The cusps of the sun around Venus appeared brighter than the body of the sun.
D shape. At 4h. 3m. 10'31s. Venus appeared to be nearly -J off the sun's limb. There was
just the slightest trace of distortion or tendency to the D form retained until the planet
was half off, but hardly perceptible.
At -Hi. llm. 15'31s. the planet was half oft'; at this stage and afterwards there was not
the slightest traces of distortion.
At 4h. IGm. 40'31s. three-quarters off.
At 4h. 23m. 30'81s. there only remained the slightest indentation to mark her
presence.
At this moment a cloud passed over the sun from left to right, and at 4h. 24in.
2'Sls. all traces of the planet disappeared from the sun's disc, i.e. final external contact at
egress took place.
ARCHD. LIVERSIDGE,
Professor of Geology,
Sydney University.
Halo.
Goulbura, 10 December, 1880.
ME. Tornaghi reports as follows : — I took the time when the line of light between Venus and
the sun's limb at egress disappeared as the time of contact.
After this I saw the halo, and it was best when the planet was half off the sun. The
outside had a greenish colour with red in it, and appeared as if formed by flames issuing from
the planet all round, and densest at the planet. The halo round the part on the sun was
different, but quite distinct and unmistakable.
TRANSIT OF VENUS. 31
REPORT BY THE REV. WM. SCOTT, M.A., ON THE TRANSIT OF VENUS
AS OBSERVED AT EDEN.
WE loft Sydney on Tuesday, November 24-th, and arrived at Eden, Twofold Eden.
Eay, the next morning. Having landed our observatory, tents, and instru-
ments, together with a good supply of bricks and cement for building piers
for the instruments, my first care was to find a suitable spot for the
observatory. I was not long in selecting an open space known as the
Market-square, on a hill overlooking both bays. This site has the advantage
of being near the telegraph line, and commanding uninterrupted views of
the ranges at some miles distance to the south and west, the wooded sides
of which I saw would afford good reference marks for the adiustments of T
Instruments.
the transit instrument in the meridian and prime vertical. The day was
nearly over before we had carted all our baggage to the top of the very
steep hill which forms the principal street. A commencement however
was made of setting up the observatory, in which we were most effectively
assisted by Mr. Ilussell, the Harbour Master, and his boat's crew. On
Saturday everything was ready, with the exception of mounting the
equatorial telescope, which was delayed in order to allow the pier to
become quite dry. An approximate meridian had been determined by sun
observations with a theodolite.
Our instruments were — the 7^-inch equatorial telescope formerly
used in the Sydney Observatory (with good driving-clock), a portable 2-inch
transit instrument, a 4J-inch equatorial telescope and a 3]-inch equatorial
telescope, the theodolite before mentioned, a clock and three chronometers.
The upper portion of the observatory was provided, besides the usual
shutter, with a frame fitting the opening, to which was attached a bag
of yellow calico, of somewhat conical form, having a hole in the smaller
end, through which the telescope and finder could pass. This bag being
secured round the middle of the telescope tube, excluded all but yellow
light, so that the whole observatory answered the purpose of a dark room
for photographic work.
This arrangement, though very convenient, was liable to be
influenced by the wind, and so to interfere with the steady motion of
the telescope. All being ready, I waited anxiously for a clear night to
enable me to make the necessary star observations for time and instru-
32 TRANSIT OP VENUS.
mental adjustments ; but so unusually cloudy was the weather that I could
get no satisfactory observations until Saturday, December 5. On the 7th
and 8th I exchanged longitude and clock signals with the Sydney
Observatory, but on each occasion was prevented by clouds from getting
more than one transit observation.
On the 7th, being a clear day, we took two sets of photographs, to
satisfy ourselves that all was in good working order, and found that by
reducing the aperture of the telescope to 3 inches the sun's edge was more
sharply defined and the reference lines more clearly distinguished.
In our trial observations of the sun several of our dark glasses were
cracked by the heat ; so finding that I could get no sufficient protection
even with the 3-inch diaphragm, I constructed one 2 inches in diameter,
which gave very satisfactory results.
In consequence of the continued cloudy weather my instrumental
adjustments were not so accurate as I wished. I was assisted one day in
adjusting the reference lines in the camera by a small well-defined solar
spot, which appeared to traverse one of the lines with great accuracy. In
order to correct any remaining error in the position of the lines, I adopted
the plan recommended by Mr. Russell of taking two photographs of the
sun, at an interval of about a minute, on the same plate, and determined
to repeat the process at every half-hour during the transit. Now, in order
to make this double image of any service, it is necessary that the common
tangents to the two images should be exactly parallel to the direction of
the sun's motion. For this purpose the telescope must remain perfectly at
rest, and therefore must not be touched during the interval.
Flashing This result appeared difficult to obtain, as the flashing shutter must
shutter. j^ ma(je ^0 cross the field a second time for the second image. The method
which I contrived, though somewhat complex, appears to be perfectly
satisfactory.
The flashing shutter, as described by Mr. Russell in his paper read
before the Royal Society on September 3, 1873, is attached to the end of a
lever, which is drawn down by an elastic band, when the other end is released
by pressing a spring. If the second image were obtained by raising the
shutter quickly by the hand at the end of the desired interval, the action
of so raising it would probably displace the telescope; or if the dome
shutter were closed, or a cap placed on the telescope, and the flashing
TRANSIT OP VENUS. 33
shutter restored to its former position and again released, there would be
the same risk and almost certainty of displacement. To overcome this
difficulty I arranged as follows : — Eor distinctness I call the end of the
tf O
lever to which the shutter is attached A, and the opposite end B. I attached
a piece of wood to the camera so as to project over B. An elastic band
secured to the camera below, and enclosing B, was tied by a string to this
projecting piece, so as to allow B to move freely within it. When a double
image is to be taken, the telescope is so adjusted, by the help of the finder,
that a little more than half of the sun shall appear in the photograph,
The driving-clock is then stopped and the photograph taken in the usual
way. The telescope remains at rest for a minute ; meanwhile the band
which pulled down the flashing shutter is cut with a sharp pair of scissors,
and at the end of the minute the string which holds the band at the end B
is cut ; B is thus drawn down and A flies up with the flashing shutter, so
that a second image is taken. As an elastic band is cut each time, it is
necessary to have as many bands round the camera at A, and as many loops
of string at the piece over B, as there are double images to be taken.
On the morning of the 9th the weather seemed promising. I Weather,
obtained clock signals from the Sydney Observatory, and by 11 o'clock we
Avcre all collected and anxiously waiting for the transit to commence.
Clouds were coming up and the wind rising, and we had reason to antici-
pate a disappointment. At the time of ingress, however, the clouds had
not yet intervened. The exact instant of first contact it was impossible to
determine. Mr. MacDonnell recorded llh. 56m. 29s. Sydney mean time
as the moment at which he became quite convinced that the transit had
commenced. I found my 2-inch aperture answer admirably, not only from
the diminished light and heat, but also from the great distinctness of the
outlines of the sun and planet. I soon became convinced that all we had
heard and read respecting the apparent elongation of the planet's disc, and
formation of what has been described as the " drop," was a delusion. For
some minutes before internal contact I could see clearly the whole of the
planet's outline ; in fact, it presented exactly such an appearance as might
have been expected from a planet possessing an atmosphere. Whilst the
direct light of a portion of the sun was shut out by the intervention of the
planet, a sufficient portion of that light reached the eye by refraction,
through that atmosphere, to render the whole outline visible. By means
of a double- wire position micrometer, I obtained a measurement of the
apparent diameter of Venus ; then, bringing one of the wires into the
34 TRANSIT OF VENUS.
position of a tangent to the sun's limb, waited until the planet seemed to
touch the other wire. This occurred at Oh. 21m. 7s., though Mr. Mac-
Donnell, who judged the same phenomenon by the eye, unaided by a micro-
meter, placed it nearly two minutes earlier, or at Oh. 19m. 24s. This I
ingress. believe to be the most important determination, being the moment of com-
plete ingress ; and I regret that the action of the wind on the telescope
rendered it impossible to keep the micrometer wire in its true position as a
tangent to the sun's limb. Still, I consider the above result to be very
near the truth. I continued to watch the planet for more than three
minutes, and saw the partial obscuration of the sun's limb by the planet's
atmosphere gradually diminishing until it disappeared altogether, when I
left the telescope at Oh. 24m. 48s. Mr. MacDonnell's estimate of the
same phenomenon was Oh. 25m. 14s. The discrepancy between Mr. Mac-
Donnell's results and my own shows how impossible it is to fix the moment
of a phenomenon of the kind, when the motion is so slow and the change
from darkness to light so gradual. The slow rate of the planet's motion
across the sun's disc may be estimated by considering that it occupied over
four hours in describing so small an arc, not far exceeding one-half of the
sun's diameter. The difficulty was still further increased by the planet's
path not being at right angles to the sun's limb, but inclined to it at an
angle of about 32 degrees.
As soon as we had concluded that ingress was complete, the 3-inch
diaphragm was substituted for the 2-inch, and we proceeded to take photo-
graphs, but in doing so we were very much impeded, and the quality of the
pictures affected by the clouds which were continually driving over the
sun's face : indeed there were very few minutes during which the sun was
not more or less obscured. Again, the action of the wind on the yellow
bag was so great that the driving-clock became almost useless, and I was
obliged to hold the telescope as best I could, with my eye at the finder,
whilst the plates were inserted and the flashing shutter released. We
made two attempts at a double image, but of course the results were quite
unreliable. On the whole we took about fifty photographs, very few of
which I fear are of any value. At one time we had to stop for twenty,
and at another time for eighty minutes, the sun being entirely obscured.
On the whole the expedition to Eden has not been so successful as I
wished it to be, and I came away under the impression that Eden, though
a beautiful spot, and in many respects a most desirable place to inhabit, is
about the worst place for astronomical observations that I ever visited.
TEANSIT OF VENUS. 35
The longitude of the Eden observatory, as determined by transits
of two stars over the meridians of Eden and Sydney, the times being
recorded on the Sydney chronograph. The weather continued so cloudy
and unfavourable during my necessarily limited stay at Eden, that I could
not obtain transits of more stars, and am reluctantly compelled to base the
longitude upon the following differences of longitude :—
h. m. s.
P c~, i Latitude and
0 5 11*01 west ot bydney. longitude.
0 5 11-13
Mean 0 5 11'07
Longitude of Sydney 10 4 50'81
Longitude of Eden observatory 9 59 39' 74
The latitude depends upon observations made with the transit
instrument in the prime vertical, and the mean result is 37° 3' 47" south.
W. SCOTT.
NOTE. — Mr. Scott returned to Sydney overland, and during the long and troublesome
journey he unfortunately lost all the papers connected with the determination of the position
of the Eden observatory. I am therefore unable to give the separate observations for
latitude.
H. C. KUSSELL.
MR. MACDONNELI/S REPORT.
Eden, Twofold Bay, 14 December, 1874.
II. C. Eussell, Esq., P.E.A.S., £c.,
Government Astronomer for New South Wales, —
Sir,
I have the honor herewith to forward my report of observations of the transit of
Venus, as seen by me at Eden, Twofold Bay, N.S.W., on the 9th December, 1874.
The telescope entrusted to my charge was an achromatic equatorially mounted by Cook Instrument.
& Sons, of York, clear aperture 41 inches, focal length 60 inches. The eye-piece used gave a
power of 98 diameters (marked 100 by the makers), and the sun's light and heat were modified
by a diagonal reflector of unsilvered glass, thus enabling the full aperture to be effective, and
a very light bluish screen was all that was necessary for the protection of the eye.
fi
b
TRANSIT OP VENUS.
Weather.
First contact.
Halo.
Halo.
Internal con-
tact.
Haziness.
Ingress.
Halo gone.
In the early morning the weather was fine, giving our party promise of successful
observations, but later in the day the sky clouded over. Towards noon it cleared up again
overhead, and the observers took up their posts. I used a chronometer, No. 419, maker,
Hornby, of Liverpool.
A little after llh. 57m. Mr. Scott called out that he saw Venus entering on the sun
I did not perceive it till about llh. 57m. 80s., when the planet was fairly encroaching on the
sun, appearing like a small notch cut out of that body.
The planet continued slowly to advance, and 12h. 4m. 59'Ss. was noted by me as the
time of apparent bisection ; a shadowy nebulous ring seemed to envelop Venus on the pre-
ceding side ; it was of lighter tint than the planet, but was decidedly perceptible, and appeared
to be about a quarter or a fifth of Venus's diameter in width.
When the ingress was about two-thirds completed the whole outline of the planet was
distinctly visible in the telescope, the shadowy envelope surrounding it very plainly. (See
plate XVIII.) Perhaps it was the solar atmosphere that served as a background to throw
the planet out into relief ; whatever was the cause, however, the phenomenon was easily seen.
Apparent internal contact was noted at 12h. 19m. 21'2s., and all attention was now
devoted to the formation and breaking of the " black drop." As Venus proceeded, the
shadowy envelope disappeared except between the planet and sun's limb, where it seemed to
fill up the space between them with faint rings concentric with the planet's edge. There was
no distinct rupture of this appearance, the light seeming to go in and out several times, and
prevented any accurate determination of the completed ingress. I marked 12h. 25m. 14'7s. as
the time, but feel now convinced that it took place at least 15s. earlier. Mr. Scott's deter-
mination was g4s. earlier than mine, but he thinks he was a little too soon, as the whole
phenomenon was too indistinct to be noted accurately. There was no abrupt breaking of the
" ligament," if it can be so called, but a gradual dissolving away.
Ingress being now completed, the camera was fixed on the large equatorial, and some
fifty photographs of the transit taken. Clouds thick and heavy covered the sun, completely
putting an end to our operations. "We had some momentary glimpses of the transit through
the telescopes, and I noted the complete disappearance of the envelope already referred to
the outline of the planet was very sharp and distinct, like a hole bored through the sun.
A heavy black cloud once more impeded our view, and egress was not observed at all
much to our disappointment.
The times of the various phenomena noted above are as near as I could judge them
but I cannot place much reliance on them, as there was so much difficulty in their deter
mination.
I have, &c.,
W. J. MACDONNELL.
TEANSIT OF VENUS. 37
MR. W ATKINS' REPORT.
Eden, Twofold Bay, 10 December, 1874.
To H. C. Eussell, Esq., Observatory, Sydney,—
Dear Sir,
As a member of the expedition sent to Eden, Twofold Bay, to observe the transit
of Venus of 1874, 1 have the honor to send you my report.
I regret that I missed observing the respective times of the external and internal
contacts on the ingress of the planet. Observations of the egress were prevented by dense
clouds entirely obscuring the face of the sun ; I can therefore only report of iny observa-
tions of the phenomena accompanying and immediately following the ingress.
The instrument used by me was an achromatic refracting telescope, of 3£- inches Instrument,
aperture, stopped down to 1J- in. The eye-piece was direct, inverting, magnifying about
120 times, and fitted with a dark glass.
I first saw the planet some half minute after the external contact was observed by the Contact.
Eev. Mr. Scott and Mr. MacDonnell. The edge of the disc formed by the planet appeared to
me clear and sharp. I did not see any halo ; but as I did not observe the planet with the
intention of noting phenomena other than the times of contact, a faint halo might well have
been observed by others without being noticed by me.
As the internal contact drew near the planet seemed to cling to the edge of the sun Elongated
and so adopt a slightly, but very slightly, elongated or oval form. (Plate XII.)
Just before the time when, from the observations of Messrs. Scott and MacDonnell,
the internal contact took place, I observed very thin lines of light flash in a direction parallel
to the edge of the sun, in the dark broad neck joining the planet with the edge of the sun.
The remarks I have before made with respect to a halo must in part be applied to what I saw
of the lines of light. I can only say that I observed the lines of light, and cannot be positive
one way or another as to the direction in which the flashes appeared to move, or whether
or not they appeared instantaneously and vanished in like manner.
The actual moment of contact I did not see, but very shortly after the time when Mr.
MacDonnell said that contact was made I saw the planet well within the disc of the sun.
As I have before mentioned, no observations were taken of the egress.
I am, <&c.,
JOHN L. WATKINS.
38
TRANSIT OF VENUS.
GENERAL REPORTS.
DK. WRIGHT'S HEPOKT.
THE morning of the 9th of December, 1874, at daylight, was calm . a heavy mist obscured
distant objects, and for some time after sunrise was so dense that the sun could be gazed at
Weather. with the naked eye. About 8 a.m. the sky began to clear, and it became evident that the day
would be fine and intensely hot. It was my intention to take the time of the internal
contacts at ingress and egress only, and during the rest of the transit to observe any
phenomenon that might present itself. To assist me in this, Mr. Russell rated my chronometer
at ll'SO a.m. by the siderial clock of the Observatory, and this was again done when tho
Instrument, transit was over. The telescope used was an 8|-inch Browning, with silvered glass reflector
of GS£ inches solar focus, provided with one of Browning's solar eye-pieces (having two
prisms arranged for single reflections). To this was attached a positive eye-piece by Ross
which gave a magnifying power of 175 diameters. The only shade required to protect tho eye
with the solar eye-piece was a light smoke-coloured glass. This was free from heat when
exposed to the full aperture of the telescope. For observing the contact at ingress and
egress the aperture of the telescope was reduced by a stop to 5} inches. In some other
First contact, observations the full aperture was used. At lib. 55m. 22s. the first contact of Venus and
the sun's limb took place, 3 minutes and 4 seconds later than the time given in the Nautical
Almanac. Definition of both sun and planet was perfect, and the margin of each was
entirely free from colour. When Venus had made a perceptible notch on the sun's edge I
looked particularly for the outline of the body of the planet, but it was uudistinguishable
from the black background of the sky. "When Venus was nearly half on the sun, I noticed a
slight form around that portion of the planet yet off the sun's disc. This brightened every
moment, so that in a very few minutes it presented a bright line of light around the planet's
edge, throwing it out in bold relief against the sky and giving Venus a stereoscopic appearance.
The planet now looked to me like a black ball suspended in the sky, that portion of the disc
which was on the sun being intensely black, whilst the remainder of the disc off the sun and
near the halo appeared decidedly lighter. The portion close to the halo was shaded with
reddish-brown colour. As Venus passed slowly on to the sun's disc, the bright halo which
at this time was about 1" iu diameter became very bright, and was observed until Venus was
fairly on the sun.
Ilalo.
Black drop.
Good defini-
tion.
Haziness.
Warned by a statement madejby the French astronomers that very possibly the " black
drop" might be absent, my attention was wholly taken up by watching the phenomena at
internal contact. The margin of Venus' [disc continued sharply and beautifully defined as it
passed on to tho sun. A slight shimmering of the solar edge might be observed at the
moment when the two outlines as it were of the sun and planet touched, and also some slight
shading of the planet's edge (something like a penumbra), but it was clear to me that there
was no " black drop," nor any such elongation or distortion of the black edge of Venus that
could be taken for it. I was so intent upon observing this that I allowed some seconds to
elapse before I recorded an observation of the internal contact at 12h. 24m. 30s. ; this I have
no doubt was half a minute after actual contact, and that it was so is proved by Mr. Eussell's
observation at 12h. 23m. 59s.
TRANSIT OF VENUS. 39
Tho planet was now fairly on the sun, the halo had entirely disappeared, although
carefully looked for with tho full aperture of 8i inches, nor could any irregularity of the
edge of the planet he detected. For an hour Venus was constantly watched in her path J^nus on the
across the sun. Her neighbourhood was closely scanned to find if possible any small speck
which might denote the existence of a satellite, but with negative results. No fresh pheno.
menon was seen. Urgent professional duties called me away for nearly an hour and a half,
but I was able at a quarter before 3 o'clock to renew my observations. Meantime tho heat of
the day had increased to 87° F. in the shade, and the black bulb thermometer in vacuo showed
124'5 F. in the sun. Tho breeze from the N.E. had freshened and was laden with moisture
which caused a slight haze in the sky, and at times some unsteadiness in definition, which,
however, on the whole remained sharp and good.
The planet was approaching the N. by W. edge of the solar disc, and when viewed with
a low power (40 diameters) appeared as a perfectly black spot on the sun ; with the full
aperture and a high power (250 diameters) the outline of Venus was still free from any
appreciable irregularity.
Determined to take the most accurate observations possible of the internal contact at Egres?.
egress, I carefully set my chronograph by the chronometer, and was fortunately enabled to
catch the precise moment of internal contact at egress, at 3h. 54m. 39'59s., Sydney mean Contact,
time ; the edge of the planet coming at that instant sharply and distinctly in contact with tho
sun's limb, it was quite as clear as at ingress that there was no black drop. The accuracy of
this observation was corroborated by Mr. Eussell at the Sydney Observatory, which is 2,300
feet north and 792 feet west from my house. His time for this contact was 3h. 54m. 39'GGs.
Ho was using the new 11 :V refractor of the Observatory, of 12 feet G inches focus, with tho
aperture contracted by a stop to G inches, and an eye-piece magnifying on his telescope
100 diameters. The edge of the planet which was in contact with the sun's limb now was
observed to assume a square form, from blunting or rounding off of tho solar cusps. This
lasted a very short time, perhaps half a minute. (Something of the same appearance was
observed at ingress before internal contact, but it was so slightly marked that it did not
excite any attention at the moment.) When Venus had still further passed off the sun, I Halo,
noticed the reappearance of tho halo around the dark body of the planet again, throwing that
portion of her disc (as at ingress) into relief against the sky. This halo gradually became
brighter, and was not uniform as at ingress, but most distinguishable on the N.E. quadrant of
the planet ; hero it presented a decided accumulation of light, especially about the centre of
the quadrant, and at this point encroached a little upon the dark outline. (See plate XXIII.) Polar spot.
The full aperture of the telescope was used, and showed the colour of the halo and the solar
light to be the same, and gave the impression that the increased light at the spot above
mentioned was dun to reflection from polar snow. The same appearance of shadings of rusty
brown colour was observed at the margin of Venus' disc as at ingress, and as she passed
onwards from off the sun the halo gradually faded until she ceased to bo visible, after the
last contact at 4h. 24m. 27s., forty-five seconds before the predicted time. Some very fine Last contact-
groups of spots were seen on the equatorial zone of the sun, but as they were far south of
the part of the transit no particular observation was taken of them.
II. G. A. WEIGHT,
40
TEANSIT OF VENUS.
External
contact.
Instrument.
MR. ALLERDING'S REPORT.
Dear Sir, Sydney, 1G December, 1874.
I have much pleasure in handing you my report of the transit of Venus as observed
by me.
The external contact at ingress I saw well defined at llh. 56m. Gs., but at the internal
contact at ingress at 12h. 24m. 14s., I saw first a haziness between the limbs (plate XIII,
fig. 3), and this turned into a cone (fig. 2), and when it had nearly disappeared it seemed to
stretch out to a fine thread (fig. 1), by which Venus seemed to be attached to the edge of the
sun — it seemed as long as -J- of the diameter of the planet — and then this line instantaneously
disappeared at 12h. 24m. 44s., but Venus was then already well detached from the sun's limb.
Had I not waited for the disappearance of the fine line I would have made the inner contact
at least 30s. sooner.
The internal and external contact at egress I cannot be very certain about, having had
so many interruptions by having to allow a great many friends to have a peep at the transit,
but I give the time as near as possible at internal contact, 3h. 54m. 35s., and external contact
4h. 23m. 48s.
I am surprised that no one in the Observatory saw anything like a drop, and my telescope
defines well, for every one that saw Venus on the sun's disk remarked its clear and sharp
definition. But I must draw your attention to my having put a cardboard cap over the object-
glass, with a 2-inch aperture, to get rid of the heat on the eye-piece. The glass I was using
has an aperture of 3 J inches, but it was not well placed, as I was obliged to use it in my back
yard which is surrounded by buildings.
I remain, &c.,
P. ALLEEDING.
P.S.— My house is situated in Hunter- street, 1,980 feet south and 1,452 east from your
Observatory. *"^
ME. BOLDING'S REPORT.
Eaymond Terrace (3 miles west of Newcastle),
10 December, 18SO.
Instrument. FOB the purpose of observing the transit of Venus I provided myself with a marine chronometer,
which was carefully rated at Newcastle, by means of the time signals sent from the Sydney
Observatory to drop the time-ball ; I hope therefore my time may be relied upon.
My telescope was a very food 3-inch refractor, stopped to If inch, equatorially mounted.
To help in securing exact time I got the services of a friend, who noted the times and any
remarks descriptive of phenomena which I made.
TEANSIT OF VENUS. 41
At the commencement the sun's edge was very unsteady and seemed to be '' boiling," Boiling,
and I did not catch the moment of first contact ; when I saw it there was a very perceptible
dent in the sun's limb ; five minutes afterwards the planet seemed to be halt' on the sun, then
appeared for an instant a tendency to a straightening of the curve, but at 12h. 13m. 40s. there
appeared a distinct shoulder on the north side (i.e. as seen inverted on the south, see fig. 1, Shoulder.
plate XXVIII). The rim was as dark as the planet itself, but unsteady, and better defined
towards the north than on the opposite point of the planet. This appendage seemed to shrink
up as the planet crept wholly on to the disc after these shoulders disappeared, and Venus came Shoulders
on with great steadiness, but at the moment I expected the complete circle came the form
shown in fig. 3, which at the time I called a parachute, time 12h. 30m. 12Js. ; upon this came a
haziness which I have shown in the same figure, and at 12h. 23m. 435s. I noted complete ingress. Haziness.
Bgrest.
As the time of egress came on the definition was very good indeed, and the sunlight was G-ood dcfini-
now sufficiently reduced, by the sun sinking to the west, to enable me to use the full aperture tl011'
of my telescope, and I saw the planet make internal contact at 4h. Om. 3'5s. without any of the
peculiarities noted during the unsteady definition at ingress. At 4h. 7m., when examining the
points of contact or cusps, I saw a silvery line of light extending partly round the west side nal°-
of the part of the planet off the sun (fig. 4) ; 30 seconds later I saw it all round that part of
Venus as in fig. 5, and I continued to see more or less of this beautiful silvery line until
•ih. llm., when I saw the last of it on the west side ; it looked like a silver edging as if caused
by refraction from an atmosphere.
The planet then passed off with nothing more remarkable than an occasional blunting
of the cusps from atmospheric disturbance, and at 4h. 20m. 7s. I noted last external contact.
The following notes are explanatory of the diagrams : — Plate XXVIII, fig. 1, the Shoulders,
shoulder noted at 12h. 13m. Fig. 2, shoulders at 12h. 15m. The angles of these shoulders were
sharply defined as I have drawn them, but at 12h. 13m. 39s. there was a quivering from shoulder
to shoulder, lasting about a second. I saw both shoulders for 2J minutes, and when the north
one in the inverted image disappeared, the other remained precisely as before for about the
same time and then disappeared. Fig. 3, the change from clear contact which I saw to this Quivering,
figure was almost instantaneous, a momentary quivering was perceptible, and then this figure
was clear and steady and remained so for 34 1 seconds, when the dullness uext the planet disap-
peared and was replaced by a clear line of light ; it was followed by a still clearer light on the
sun's edge, then the black centre disappeared ; the whole change scarcely occupying more than
one second of time, and at 12h. 23in. 43£s. the sun's limb was clear. Fig. 4, from first contact
at egress the planet's outline was seen distinctly for G minutes and then it disappeared, but a
minute later I saw it by the very delicate line shown in this figure. Fig. 5, the slender silvery
line, as seen 7J m. after first contact at egress, lasted, more or less, untill llm. after that time,
when only the first part seen remained, and a minute later this was lost.
IT. .T. BOLDING,
Police Magistrate.
42
TEANSIT OF VENUS.
Weather.
Instruments.
Ingress.
Internal
contact.
No drop.
Passage.
Last internal
contact.
MESSRS. BELFIELD AND PARK'S REPORT.
Eversleigh, Armidale, 9 December, 1874.
THE day was cloudless and free from haze, the air favourable for observation, and at the
commencement of the transit definition of the sun's limb clear and sharp.
Instrument used, 4j-inch refractor, by Cooke, equatorially mounted, no driving-clock ;
full aperture used, power 130, with first surface reflecting solar eye-piece.
Chronometer showing Sydney mean time nearly and losing rate supposed to be l'5a
daily.
Ingress.
External contact not seen.
At 12h. 14m. 45s., when the planet appeared to be about f on the sun's disc, the following
third of the planet was slightly elongated and its limb distinctly illuminated, giving the
appearance of a thin crescent and thus exhibiting the whole disc of the planet most clearly.
(Plates VIII and XIX.)
At 12h. 15m. 45s., these appearances becoming more distinct, the air being very good
and limb of sun and whole outline of planet being remarkably well defined.
The elongation of following side of planet disappeared as internal contact approached.
Internal contact at 12h. 20m. 22s., discs being tangential, no appearance of drop, shade
ligament, or other distortion.
At 12h. 20m. 30s., light of sun visible all round the planet, limbs of both bodies stil
sharply defined and clear.
While Venus was advancing to about 5 of her own diameter upon the sun, a faint
tremulous shading was seen between the edge of the planet and the limb of the sun (both
bodies being very sharp in outline), which disappeared so gradually that it could uot be said to
have been obliterated at any particular instant. (Plates IX and XX.)
When fairly on the sun the body of the planet appeared intensely bluish black in centre,
becoming of a gorgeous deep blue towards the circumference, which remained well defined and
sharp. No appearance of satellite, spots, or nebulous outline. (Plate VIII.)
At 3 p.m., sun boiling, limb of sun and circumference of planet seething, latter losing
its blue colour and becoming blacker.
Egress.
When Venus approached the sun's limb a shade similar to that observed at ingress was
caught, but not so plainly ; it in no way interfered with the sharpness of outline of either body.
(Plates IX and XX.)
At 3h. 52m. 23sec. the shade no longer visible ; sun's light still visible all round the
planet. At 3h. 53m. 12s., internal contact, edges fairly defined, but not so clear as at ingress
No drop, ligament, or other distortion visible. At 3h. 56m., preceding limb of planet illumi-
nated on one-third of its arc.
Bisection of planet estimated at 4h. 7m. 22s., external contact at 4h. 21m. 51s., definition
uncertain, limb of sun running like a mill-race.
Three drawings (Plates X,XIX and XXI), showing northern limb of sun and illuminated
edges at ingress and egress.
TEANSIT OP VENUS. 43
Plates IX and XX show the tremulous shading just before it disappeared and also the
colour on the planet. In the telescope the blue was deep, pure, and utterly beyond practica^
representation ; the same remark applies to the other effects depending upon colour. The
tremulous shading is nearly accurate, but there was a quivering motion, like that of heated air
on a hot day, whicli cannot be imitated.
Plate X shows the halo or illumination at egres>r.
A. W. BELFIELD.
A. J. PAEK.
MR. BELFIELD'S REPORT — ADDITIONAL NOTES.
My dear Sir, Eversleigh, Armidale, 24 December, 1874.
I wish to thank you for your letter of the 15th inst., and have much pleasure in
replying to your questions and in forwarding coloured sketches which represent what I saw
as well as I can transfer my recollections to paper.
The illumination of the following limb of the planet at ingress seemed to be equal in
breadth all round, and was bright enough to give an appearance of elongation to the part of
the planet not on the sun's disc ; it seemed to be outside the limb, which was quite distinct
its breadth I see has been estimated at 1" — I should have thought it was nearer 2" — when
Venus was -J on the sun's disc, but I have no experience in making measurements of the .kind
I saw nothing like margin or shading round the part of the planet on the sun's disc.
The blue colour on the planet was the deepest prussian blue, black in centre, lighted
towards the edge, but the lightest part was a very deep blue. It did not in the slightest degree
mar the clear definition of the planet's disc or extend beyond it, and was not in the least like
the violet colour seen round Venus at her brighter phases when viewed against the evening
sky. The colour is fairly represented in Plates VIII and IX. There was no trace of colour
visible when looking at sun-spots with same diagonal, eye-piece and shades.
The colour was very vivid during the earlier part of the transit, when the air was very
steady ; during the latter part when the sun began to boil the planet to my eyo was a dead black
(Plate X) ; others with me said they saw the blue colour still, to me it was not obvious but
had to be looked for ; there was certainly a very great difference in colour during the earlier
and later parts of the transit. I did not notice the film of cloud you mention.
At egress the illumination was seen on only a part of the planet's disc off the sun. At
the intersection of the limbs of Venus and the sun on the northern side of the planet (direct
image) it was broader than at any part during ingress, but thinned off to nothing rapidly, and
the rest of the planet's outline was not distinguishable from the black background of the sky.
"When Venus was about i off the sun the illumination extended over about -J- of the arc
of the planet outside the sun, but as the planet's disc left the sun the extent of illumination
did not increase accordingly, but was confined to about the same extent of outline as when
first noticed. The air at egress was by no means good.
A. W. BELFIELD.
[Forty-one plates.]
Sydney : Charles Potter, Government Printer.— 1892.
PL AT El
Jt not circular; slight bulge on S.Wpart
K m sec.
t 23 57.30 Sydney mean time .
w-
Haio on disc of pknet at
h m sec
0.7.0 Sydney m. t.
s
Ring of light around following limb
Ji m sec
of planet at 0 . S. 30 Sydney m. t
w —
k . m . sec.
of light at 0.19.30
Sydney m. t.
of faruus 1874
WoooLforoL N.SW.
Mr Vessels Observations.
Y
PLAr
T tr i, m S6C
Ingress "Apparent" internal contact at 0.23.47.07 Sydney -mean time.
Limbs of planet and sun tangential and ring of light separating planets disc and sky
Transit of
1874
Woodforoi N. S. W.
M1" Vesseyls
TE III
-i- Km. sec.
ingress at about 0.24.0 Sydney mean time.
Dusky ligament between planet and sky divided Joy the ring of light
Transit of V&nws 1874.
WoocifordL. I S. W.
Mr Yesseys Odserrcubwns
PLATE IV
vV-
1. . m . sec
Egress "Real" internal contact at 3. 54.25.47 Sydney mean time.
Sunlight cut off and light of ring only remaining between planets disc and sky.
Transub of Venus 1874
Woodford N.S. ¥
V&sseys Ot>serva,tvon>s.
PLATE V
w-
K m sec
Egress at 3 54. 37.5 Sydney mean time.
Cusps of sunlight separate slightly thickened at extremities and connected by the
white light of the ring.
of V&TUJUS. 1874
Woodford N S.W
V&ss&y's
ni
i j
w
in sec
Egress_"Apparent: internal contact at 3.54.46.41 Sydney mean time.
-JDS of planet and sun tangential and ring of light slightly overlapping limb of sun
Transit of Venus 1874
WoocLford-, K S W.
Mr V&ss&y's Observations
Irbgr&ss
s
i
PLATE Vn
Egr&ss
Globular appearance of planet
j -30 30 Sydney mean time.
Irregular shape of planet and ring
h m sec
of light at 4. 2.30 Sydney rn t,
Planet copper colored and glo]
at 4 9. . Sydney m t
Tran-siZ- of
.
Vianet not Circular at 4 . 17 0
Sydney m t
1874
Wood/brd, IT'S. W.
Ingress -showing elongation, illumination and colour
of Venus 1<S74
KS. W.
MrA.H.BdfidcL's Observations
••
Ingress showing color of planet and shade between the limbs.
Transit of Veruis /874
W.
M?AffJ}eLfielt£s Observations,
PLATE X
Egress_showing partial illumination.
of Ye/rums 1874
N. S.
MrA.H.B&lfb&Us Observations.
PLATE XI
Flash of Light on outer edge of Planet at Egress.
Transit of Venus 1874.
PLATE XII
Planet elongated
Transit of Verui*s 1874.
N.3.W.
MrWatkins Observ&ttons,
PLATE XIII
Black Drop
of !/&ruzs 1874
tf.S.W.
PLATE XIV.
The Black drop at ingress and egress.
Copy off how frcnr. Janssen plate Ne5 wkucJi was taken when, £h& black drop wctf seen,
(Magnified, five, duzm&Lers)
-TT
.CA.
•
Venus seen with a narrow fringe of dull red light.
of Venus 1874.
MrG.D. lMrs& Observations.
PLATE XVI
Halo on Sun
Transit, of farms 1874.
Cap,, Onslow's Observations.
X
PL,
o
CO
f-j
^
PH
§
o
"(3
g
§
PLATE XVIII
Halo around planet.
of Venus 1874
MS. w..
9 Observations.
Shewing positions of illuminated edges.
of Ven/ws 1<374
M" ' A.J.Parks Observations
PLATE XX.
Ingress shewing blue colour of planet and tremulous shading
of l&ias 1874
N.s.w.
PLATE XX!
Egress Shewing illumination of proceeding limb.
Dark smoky neutral shade used.
of Vervuus 1874.
N.S.W
MrA. J. Park's Observations.
R
X
g
<0
rC5
^
Sv
t
•5
s
b
PLATE XXIII
Halo and Polar Spot seen at egress
Transit/
1874
N.S.W.
Observations
D
ro
i_i
o
o
tq
a
j
P-.
JD
X
O CD
cx C
w fa
'o 9
o -5
^
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^
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8
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03
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CD
I
ol
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CD
(D
CO
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0,
PLATE XXIX.
• \
- -S
I
j' V-
^l
PLATE XXX.
&
g
PLATE XXXI.
cc
o
f—
CQ
O
UJ
z
Q
oo
PLATE XXXII.
LARGE EQUATORIAL, SYDNEY OBSERVATORY.
OBJECT GLASS 11} INCHES.
PLATE XXXIII.
PHOTOHELIOGRAPH,
WOODFORD.
PLATE XXXIV.
CO
UJ
o
CO
UJ
cT
cc
o
U-
Q
O
O
CO
3
z
UJ
U-
o
CO
cc
H
PLATE XXXV.
Q
OC
O
u.
Q
O
O
GO
OS
—
cc
O
u.
o
PLATE XXXVI.
UJ
CO
z
u
Q
o
U-
o
PLATE XXXVII.
7HNCH EQUATORIAL USED AT EDEN.
PLATE XXXVIII.
6-INCH EQUATORIAL USED AT GOULBURN.
PLATE XXXIX.
» •§ 1=
PLATE XL.
GENERAL LIBRARY
UNIVERSITY OF CALIFORNIA— BERKELEY
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