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Full text of "Observations upon the late great comet and transit of Venus, made at Crowborough, Sussex, in the year 1882"

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^i^3iSi 



PHILLIPS LIBRARY 



HARVARD COLLEGE OBSERVATORY 



THE EQUATORIAL TELESCOPE 

AT THE OBSERVATORY, CROWBOROUGH, 

SUSSEX. 



OBSERVATIONS 



UPON THE LATE 



GREAT COMET 



AND 



TRANSIT OF VENUS, 



MADE AT CROWBOROUGH, SUSSEX, 

IN THE YEAR 1882, 

BY 



WITH ILLUSTRATIONS. 



LEWES : 
H. W. WOLFF, "SUSSEX ADVERTISER OFFICE.'* 

1883. 



I 



% -V 



THE GREAT COMET OF 1882. 



HE general interest which has 
been excited by the appearance 
of the late great comet, induces 
me to furnish a few particulars 
respecting it which I trust may 
be interesting to those who regard 
these mysterious astronomical 
visitors with the attention which 
they deserve ; for a mysterious object a comet stillTemains, and 
notwithstanding the rapid advance of astronomical science, 
we as yet know but little of their composition, use, and 
destination, in the grand economy of Nature, whose power 
and laws are never permitted to work by chance. Although 
the time for exciting great alarm and dread, at the appearance 
of a remarkable comet, is passing away, yet it has lately been 
witnessed, with regret, that even at the present day persons 
have not been wanting who, for the sake of notoriety or gain, 
have issued to the public the most absurd speculations respect- 
ing the probable injury which this earth, and everything upon 
it, might sustain at the approach of, or contact with, one of 
these celestial visitors. Let us hope that, as education and 
intelligence increase, the spectacle will only excite wonder 
and admiration of the Power by whom it has been created. 
The first announcement of the approach to us of the late 



4 The Great Comet op 1882. 

magnificent comet came from M. Cruls, of Rio Janeiro, to 
Lord Crawfurd's observatory at Dun Echt, near Aberdeen. 
It was first noticed in Brazil on Sept. 12, but had been seen 
previously by Dr. Gould, at Cordoba, on the 6th, and by Mr. 
Finlay at the Cape of Good Hope on the 8th, and it was 
further reported as being visible there to the naked eye in 
daylight. The first person who saw it in this country was, 
1 believe, Mr. Common, of Ealing, when it was very near the 
sun about the time of perihelion passage. It happened, most 
unfortunately, that the weather during the latter part of 
September was exceptionally gloomy and unfavourable for 
astronomical observations over the greater part of the United 
Kingdom. The first spectroscopic observations informed us 
of the important and interesting fact, that the sodium line 
was displaced towards the red end of the spectrum, which at 
once indicated that the comet was receding from the earth. 
The brightness of the nucleus must have been enhanced by 
the large quantity of sodium which it may have temporarily 
absorbed while in close proximity to the sun, even if >it were 
not an elementary constituent of the comet itself. It was 
further noticed that, as the comet receded from the sun, 
this sodium line became fainter, and finally gave way to those 
of the hydro-carbons which have been observed to be the 
more usual and prominent lines in the spectra of late comets. 
I will also observe that the only previoiis instance of the 
visibility of a sodium line in a comet's spectrum occurred in 
that of the comet Wells a few months since. This would 
almost seem to lend countenance to the idea, that a kind of 
periodicity in apparitions of comets of peculiar types of 
chemical composition may exist. 



The Great Comet of 1882. 5 

No sooner was it observed in England than a host of 
conjectures arose as to whether this fine comet was a stranger 
or not, and the wildest theories respecting it obtained credence; 
in fact, among a certain class, the whole solar system was 
supposed to be in imminent danger of entire destruction. To 
astronomers, generally, the comet was found to be a great 
mystery with reference to the period of its orbit, and an idea 
was hastily entertained, at first, by Prof. Boss, of America, 
and others, that it might probably be a return of the great 
comet of 1843 ^^^ 1880. A little careful study sufficed to 
decide that, however nearly corresponding in some parti- 
culars, yet the identity of the orbits of those two comets with 
that of i88:z (so far as observations had already been made) 
could not be established. The announcement of this fact 
succeeded in dispersing many of the sensational ideas, in 
relation thereto, which were becoming only too prevalent. 
Moreover, before such a decision could be arrived at, it would 
be imperatively necessary to examine the important observa- 
tions which would in due time reach us from the southern 
hemisphere. It has rarely happened that very accurate 
observations of the position of any comet before, as well as 
after, perihelion passage have been possible, but in this instance 
it was accomplished in a very satisfactory manner both at the 
Cape of Good Hope and in America. 

In the first computations of its orbit considerable difficulties 
arose, not only on account of the supposed, and very probable, 
disturbing influence which it had sustained in consequence of 
its abnormally close proximity to the sun at perihelion, but 
on account also of the peculiar character of its nucleus. 
During the second week in October information reached this 



6 The Great Comet op 188:2. 

country firom the Cape, that Mr. Finlay, assistant at the 
Observatory there, saw the comet on Sept. 8, three days 
before it was seen in Brazil, and that he subsequently followed 
it with his equatorial telescope to the very instant of contact 
with the sun's edge, or limb, which was, without any doubt, 
an unprecedented astronomical achievement. 

The intensity of the light of the nucleus must have been 
very great indeed, and probably equal to that of a correspond- 
ing area of the sun's surface as it approached, and entered 
within, the precincts of the solar corona, and fully accounted 
for its visibility to the naked eye in daylight. 

As time went on, and the number of computations of its 
elements increased, it became apparent that it could neither 
be the return of the great comet of 1668, nor, as had been 
considered by some, identical with that of 1843 or 1880, 
while there were others who supposed it might be a return of 
the comet of 1680. Little doubt, however, was at last 
entertained of the stranger being a comet whose orbit is best 
represented by a very elongated ellipse, having a period of at 
least 700 years. The present generation has therefore been 
fortunate in witnessing the apparition of this grand comet. 
It was observed very generally on the Continent during the 
last week in September, particularly at Nice, Florence, and 
Palermo, where the weather at this time was very favourable 
for its examination. 

Both in the northern anil southern hemispheres it excited 
the greatest interest, both on account of its magnificent 
appearance as well as the difficulties which presented them- 
selves to astronomers in calculating its orbit. It appears 
very probable that, as we have said, it has a period of more 



The Great Comet of 1882. 7 

than 700 years, but estimates of it have been given which 
vary between 6^% and 4,070 years ! 

Upon the supposition, then, that the period of its orbit 
ranges between 700 and 800 years, we naturally refer back to 
the eleventh century, and endeavour to recognise its previous 
appearance during that period. The records of many great 
comets which were visible at, and about, that time are unfor- 
tunately very incomplete, and probably inexact ; but a brief 
notice of some of them, gleaned from a variety of sources, may 
perhaps be acceptable. I imagine that very few which were 
visible to the naked eye escaped some kind of record, and 
chiefly, perhaps, on account of the apprehended dire mis- 
fortunes of which credulous people believed them to be either 
the origin or the portent. 

Sir Edward Sherburne, in his " Sphere of Manilius,'' has 
given a long and very interesting catalogue of comets, which 
have appeared between B.C. 400 and A.D. 167:2; his book 
being published in 1675. I will now give an extract from 
his list respecting the appearance of some conspicuous 
comets which he has recorded as being visible during the 
three centuries, whereof that wherein our recent visitor last 
appeared may possibly have been the third. 
A.D. 800. A fine comet appeared before the time that 

the Empire of Rome was transferred to Charle- 
magne. 

„ 814. In November, immediately before the death 
of Charlemagne. 

„ 837. A comet appeared at Easter; lasted twenty- 
five days. It had a retrograde motion, and 
disappeared in the head of Taurus. 



8 The Great Comet of 1882. 

A.D. 838. A comet was seen in the autuma before 

sunrise, and it was dreadful to behold. 
„ 874. A comet appeared, and lasted a month. It 

was dreadfully red and fiery^ and projected a 

long train of light. 
f> 875. A comet appeared on the sixth of June, and 

lasted a few nights ; shining by day as well 

as night. Extraordinarily sparkling, and more 

than usually red and flaring, with long hairy 

beams. 
,, 88:2. A large comet appeared, with a bush or tail 

of great length. 
jy 908. A comet appeared more than ordinarily 

bright. 
945. A comet appeared of a wonderful magnitude^ 

scattering about fiery rays and beams. 
962. A comet of an unusual grandeur was seen in 

Italy. 
975, One appeared in August, which was visible 

for eight months. 
999. During the evenings, at the beginning of 

December, a comet was visible of a most 

stupendous magnitude. 
„ 1003. About the end of May a comet appeared in 

the south, having a terrible aspect, 
„ 10J7. A comet more strange than usual appeared 

in the constellation Leo, and lasted four 

months. 
„ 104^. A comet appeared on the sixth of October. 

It appeared in the morning, and lasted a 



» 



9} 



}} 



ii 



m 



The Great Comet op i88:j. 9 

months moving from east to west. It had 
long flaming hairs. 

I find the following notices of comets in the Anglo-Saxon 
Chronicle, referring to the same period : — 
A.D. 892. And in the same year after Easter, about 

the Rogations (May 29) or earlier, appeared 
the star which in Book-Latin is called Cometa. 
Some men say in English that it is a long 
haired (feaxed) star, because there stands a 
long ray from it, sometimes on one side, some- 
times on each side. 

„ 905. This year a comet appeared on the xiiith of 
the Kal. of November (Oct. ao), 

ff 995- ^^ ^^^^ y^^ appeared cometa the star ; and 
Archbishop Sigerie died. 

„ 1066. In this year King Harold came from York 
to Westminster, at the Easter, which was after 
midwinter, in which the King died ; and Easter 
was then on the day the xvii of the Kal. of 
May (April i6). Then was seen over all 
England ^uch a sign in the heavens as no man 
ever before saw. Some men said that it was 
the star cometa, which some men called the 
hairy star; and it first appeared on the eve of 
Litania Major, the viii of the Kal. of May 
(April 24) and so shone all the seven nights. 

„ 1097. Then at St. Michael's mass the iv of the 
nones of October (Oct. 4) there appeared an 
extraordinary star shining in the evening, and 
soon going to its setting. It was seen in the 



lo The Great Comet of 1882. 

south-west, and the ray that stood from it 
seemed very long, shining south-east; and 
almost all the week it appeared in this wise. 
Many men supposed it was comet. 
Niccphorus Callistus, too, in his ecclesiastical history, 
mentions a very remarkable comet which appeared about 854, 
just after the death of Alaricus. It must have had a wonder- 
ful appearance, being visible at midday, and lasting four 
months. The representations of many of the ancient 
comets, which Sir Edward Sherburne has given in his work, 
are so very extraordinary that it becomes difficult to under- 
stand what was really seen, or supposed to be seen, and so 
also are the names which were given to them. Thus we 
have the "Horse comets, the sword-shaped, the lamp- 
shaped, the hairy, the bearded, the horned, the tubiform, the 
elliptic, the round, the spear-shaped, the pyramidal, the 
monstrous, &c." 

The opinions of the ancients respecting the composition 
and nature of comets are no less quaint. Thus Aristotle 
asserted that the bush or train of a comet was an exhalation 
set on fire, in a more rare and less condensed matter than 
its head, and diversified according to the disposition of the 
matter which feeds its flame. 

Seneca conceived the " cauda,^^ or bush, to be no part of 
the comet, nor a flame, but the rays of light which the 
comet, by its native vigour, sends forth. Apianus thought 
the bush, or tail of a comet, to be nothing else but the rays 
of the Sun transmitted through the semidiaphanous head 
thereof, as it were through a globe of glass. Tycho Brah^ 
thought the tail to be nothing else but the beams of the sun 



The Great Comet of i88a. ii 

penetrating the head of the comet. Kepter has given a 
double reason for the phenomenon of the tail. He supposes, 
first, that the tail is enlightened by the Sun's beams passing 
through the body of the comet ; and, secondly, he makes 
the comet to exhale a certain lucid matter from its head only 
in different rarity. Gralilei thought that the tail of a comet 
is of its own nature, straight, as being produced by the Sun's 
beams, but appears crooked to us when near the horizon. 

Cysatus, seemingly following Apianus, conceived the tail 
of a comet not to be a flame, but a cone or pyramid, made 
by the Sun's beams transmitted through the head of the 
comet in the same manner as the Sun's light, passing 
through a hole or convex glass, illuminates a chamber, 
which, he says, is done partly by refraction, and partly from 
the polyangular sides of Corpuscula that form the nucleus. 
The celebrated Ricciolus held the notion, at first, that the tail 
of a comet is of the same substance as the nucleus, and 
shone by its own light propagated from its head, the face of 
which is always '^ converted to the Sun like a Heliotrope, 
or as a magnet to the Pole." That the more perfect part 
always respects the Sun, and the other part turns from it ; 
also that it has divers shapes and figures, according to the 
several species of comets, and the diversity of its matter and 
configuration. Secondly, he held it probable that the train 
of a comet is a multitude of most subtile Corpuscula in the 
air, or rather, flying about the head of a comet, not such as 
we see ^^ through a chink dancing in the sunbeams,'^ nor like 
those exhalations which form the twilight, but much more 
subtile and higher, nor apt by reason of their smallness, their 
little opacity, and great distance from the Sun, to be discerned 



12, The Great Comet of 1882. 

by us through the reflexions of the Sun's beams unless very 
strongly illuminated ; that^ that strong illumination is made by 
the collection of the Sun's rays, by the power of refraction into 
one, though not precisely after the same manner as they 
unite, after their trajection, through a sphere of glass. He 
likewise thought the head of the comet to consist of divers 
minute bodies *' Homogenial,'' of difierent angular forma- 
tions. Hence by the benefit of their various surfaces passing 
in divers manners through the nucleus, according to the rules 
as well of refraction as reflexion, come forth much more 
multiplied and collected together than otherwise they would 
do if they passed not through the nucleus or were not 
refracted. These opinions of Ricciolus assimilate very much 
to some modem opinions as to the meteoric constitution of 
comets. To the above hypotheses of the nature of comets 
might be added those of Des Cartes, Gassendi, and Hevelius ; 
the relation of whose ideas respecting them would be too 
long for insertion here, and I would refer the reader to the 
respective works of those great astronomers. 

Coming down to our own time, and theorising in the light 
of our improved modern methods of investigation, we find, 
nevertheless, various interesting ideas broached as to the com- 
position and formation of the tails of comets. A very in- 
teresting chapter on this subject will be found in Mr. Proctor's 
" Science Byways,'' from which I purpose extracting a few 
paragraphs. '^ Prof. Tyndali was led by his researches upon 
light to a theory somewhat similar to the lens theory, but 
altogether better worthy of careful consideration. He had 
noticed during his experiments on the chemical action of 
light, that almost infinitesimal amounts of matter when 



The Great Comet op i88a. 13 

fe diffused in the form of a cloud, can 'discharge from it by re- 

iB3it flection' an astonishing body of light Let us see, 

tioo however, how Tyndall associates his actinic clouds with 
as : comets and their appendages. After briefly describing the 
ss. : diflSculties which surround cometic phenomena, he proceeds 
){k to present 'a speculation which seems to do away with all 
• fe these difficulties, and which, whether it presents a physical 
pas£ verity or not, ties together the phenomena exhibited by comets 
be:: in a remarkably satisfactory way.' The theory is, that a 
h D^ comet is composed of vapour decomposable by the solar light, 
^w: the visible head and tail being an actinic cloud resulting from 
re I such decomposition ; the texture of actinic clouds is demon- 
strably that of a comet. The tail is not projected matter, but 
matter precipitated on the solar beams traversing the 
^Q0 cometary atmosphere. It can be proved by eocper intent that 
,yeiiis this precipitation may occur either with comparative slowness 
[,ett along the beam, or that it may be practically momentary 
{Q tt throughout the entire length of the beam . » . as the comet 
wheels round the tail is not composed throughout of the same 
M matter, but of a new matter precipitated on the solar beams, 

which cross the cometary atmosphere in new directions 

The tail is always turned from the Sun, for the following 
reason s two antagonistic powers are brought to bear upon 



VP 

.tioii 



ti^ 



^{Q{^; the cometary vapour — the one a chemical power tending to 
^ fjr form the invisible cloud, the other a heating power tending to 
^poi dissipate it into invisible vapour. 'As a matter of fact, the 
Sun emits the two agents here involved. There is nothing 
hypothetical in the assumption of their existence.' *' 

That visible cloud should be formed behind the head, or 
in the space occupied by the head's shadow, it is only neces- 



- b^ 



)D». 



14 The Great Comet of 1882. 

sary to assume that the Sun's heating rays are absorbed more 
copiously by the head than the chemical rays. This augments 
the relative superiority of the chemical rays behind the bead^ 
and enables them to form the visible cloud which constitutes 
the tail. The old tail, so soon as the head by its onward 
motion ceases to screen it, is dissipated by the Sun's heat. 
The dissipation f like the formation^ not heing instantaneous, the 
curvature of the tail and the direction of the airvature are 
accounted for, Tyndall also remarks that "the cometary 
envelopes, and various other appearances may be accurately 
reproduced through the agency of cyclonic movements intro- 
duced by heat among the chemical clouds with which the 
theory has to deal." Again, he suggests that "there may be 
comets whose vapour is undecomposable by the Sun, or which, 
if decomposed, is not precipitated. This view opens out the 
possibility of invisible comets wandering through space, per- 
haps sweeping over the earth and affecting its sanitary con- 
dition without our being otherwise conscious of their passage. 
As regards tenuity, 1 entertain a strong persuasion that out 
of a few ounces (the possible weight assigned by Sir John 
Herschel to certain comets) of iodide of allyl vapour, an 
actinic cloud of the magnitude and luminousness of Donati's 
comet might be manufactured.'^ But there is also the repul- 
sion theory of comets' tails, in favour of which Donati's comet 
afforded apparently decisive evidence. The great curved tail, 
which formed so remarkable a feature of that comet, presented 
the usual appearance of being formed by the sweeping away 
of the outer parts of the envelope by a solar repulsive force ; 
and its well-marked curvature showed that, if such a repulsive 
force had really acted, the rate at which it swept the matter 



The Great Comet of 1882. 15 

of the tail outwards, though very rapid, was by no means so 
rapid as the motion of light. The tail, visible at any given 
time (during the chief splendour of the comet), was the work 
of several days, not of a few minutes, whether the repulsion 
theory or Tyndall's were the true explanation. Upon re- 
viewing the two theories Mr. Proctor seems to consider that 
the repulsion theory is the more probable. There is also the 
meteoric theory of comets, but Mr. Proctor says that so far 
as is known it is the head only of comets to which that 
theory applies. It is known that meteors follow in the tract 
of the head, that is, in the same orbit j but the tail does not 
at any time agree in position with the orbit, and we have no 
sufficient reason, from observation, to suppose that the tail 
consists of meteoric matter, although of course it is quite 
possible that the repulsion by which the tail seems to be 
formed may carry into the tail matter of the same sort as that 
out of which the meteoric attendants are formed. 

I will conclude this subject with the remarks long since 
made by Sir John Herschel, that — ''There is, beyond 
question, some profound secret and mystery of nature con- 
cerned in the phenomena of comets' tails. Perhaps it may 
not be too much to hope that future observation, borrowing 
every aid from rational speculation, ground on the progress of 
physicial science generally (especially those branches of it 
which relate to the ethereal or imponderable elements), may 
ere long enable us to penetrate this mystery, and to declare 
whether it is really matter, in the ordinary acceptation of the 
term, which is projected from their heads with such extrava- 
gant velocity, and, if not impelled, at least directed in its 
course by a reference to the sun as its point of avoidance/' 



i6 The Great Comet op i88a. 

THE COMET OF i88a. 

I will now proceed to give a summary of my own observa- 
tions^ at Crowborough, of the late great comet, technically 
known as Comet b, 1882. The extremely overcast condition 
of the sky, which continued for several days after I had re- 
ceived intimation of its appearance, prevented me ftom 
having an opportunity of examining it until the early morning 
of Oct 4th. I thought that its general appearance was 
grander than Donati's, which became visible in 1858, and 
that its whole aspect, and particularly that of its tail, was 
more brilliant to the naked eye than the corresponding details 
in the comet of 1861. The tail was about 25 degrees long {i.e., 
covered a space in the sky equal to fifty moons placed edge 
to edge), and broadest at its extremity, which was somewhat 
bifurcated, extending in a line nearly parallel with the equator, 
and a little south of the well-known star Alpha Hydras The 
engraving (Fig. i) represents its general configuration 
as seen in a good opera glass ; but a week afterwards the 
extremity of the tail was more bifurcated than is here repre- 
sented, and so continued during subsequent observations for 
a considerable time. 

I had not another opportunity of seeing it until the morn- 
ing of the loth, when, in consequence of observing it some- 
what earlier, the tail had a still more brilliant appearance, and 
exhibited altogether a very imposing spectacle. Notwith- 
standing, however, its brilliance, a few small stars were visible 

through it. As regards the appearance of the nucleus, to 
the naked eye it might have been considered equal to a star 

of the second magnitude, while in the telescope it looked 

oval or rather pear-shaped. 



t J 



*• 



it 






* i 



.♦• \ .<. 



GENERAL VIEW OF THE COMET AS SEEN 
WITH AN OPERA GLASS. 



The Great Comet of 1882. 17 

On Oct. 13th the atmosphere was by no means clear 
enough for good observation, being very tremulous and hazy ; 
nevertheless, I obtained a short view of the comet through 
some thin clouds, and noticed that the nucleus instead of 
being oval, or rather pear-shaped, had become somewhat 
columnar, while a flickering light was observed along its 
length in the direction of the axis of the tail. From the ac- 
counts which I had seen respecting its visibility during day- 
light, I fully expected to have seen the nucleus after sunrise, 
but in this I was disappointed, as the whole phenomenon 
was very impatient of daylight. The weather, subsequent to 
the above observation, continued very unfavourable to the 
morning of the 20th, and even then, it was not until the 
dawn had considerably advanced that the clouds cleared away 
sufficiently to enable me to get a sight of the nucleus, in 
which I discovered that a further change had taken place since 
my observation of the 13th. Although definition was much 
interrupted by a thin layer of cloud, yet I could perceive that 
the nucleus was broken up into at least three portions, the 
central one of which was the brightest and largest j also that 
the nucleus had become narrower, longer, and relatively 
brighter, with the three points of condensation noticeable 
within it. The southernmost of these points was extremely 
faint, and required some attention to be seen at all. 

On the morning of Oct. 23rd I had a better view of the 
comet than on any previous or subsequent occasion — the time 
was about 4h. 30m. L.M.T. The atmosphere was very 
diaphanous, and the definition extremely good. Notwith- 
standing these very favourable circumstances I thought that 
the brilliancy, both of the nucleus and the tail, had slightly 



1 8 The Great Comet of 1882. 

diminished. The former was still visible to the naked eye as 
a fourth or fifth magnitude star^ while the length of the 
latter was reduced to about twenty degrees, and its width, at 
the extremity, to less than two. The nucleus proper had 
become very linear, and had upon it f(mT distinct points of 
condensation, a representation of which I have endeavoured 
to give in the subjoined sketch. See Fig. a. 

The above woodcut must not be supposed to give an exeunt 
view of the comet's nucleus, but rather a diagram of its struc- 
ture, as it was found very difficult to reproduce, by means of 
a wood block, such a nebulous object. The points are, there- 
fore, rather exaggerated in size, as well as the linear character 
of the nucleus itself, but it will serve to illustrate the nature 
of the wonderful disruption, and relative distance, of the several 
portions. 

'a' was the most difficult point to discern, 'i' was by 
far the brighest and largest of all ; ^ c' was very considerably 
less bright than *bf while 'd' was nearly as faint an object 
as ' a/ and not quite so large. The frequent flickering of 
the light of the nucleus was particularly apparent both to the 
naked eye and in the telescope. 

After the lapse of another week, viz., on Oct. 30th, I had 
one more opportunity of observing the comet, but found that 
the presence of moonlight considerably diminished its bright- 
ness. The nucleus, however, was quite visible to the naked 
eye, and shone brightly in a large opera glass. Point ^ b ^ 
still maintained very much of its brightness, but the points 
^a/ ' Cy ^ dj were scarcely visible ; in fact, ^ a ^ could no longer 
be seen. The nucleus maintained its linear form, but the 
comet's more interesting features were much less distinct. 



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.i ' . ' 



' . .1 



J. 1 • it" t, ■ ! 1 '-If 

J 



THE NUCLEUS, OR HEAD, OF THE 
COMET, MAGNIFIED So TIMES. 



The Great Comet of 1882. 19 

Throughout the length of the tail was a nearly central space, 
the southern side being the brighter of the two. It may be 
as well to mention that, on Oct. 8th, Dr. Schmidt, at Athens, 
discovered a small comet which was supposed to have had 
some connection with the larger one, as it was travelling in 
a very similar path, but no subsequent observations have con- 
firmed this supposition. It is possible there may have been 
some connection in past ages. 

During the evening of January 27 th, 1883, Mr. Common, 
of Ealing, with his large reflector, observed the comet, and 
found it presenting the appearance of an elongated nebula. 
Upon applying a somewhat higher power he noticed that there 
-were five points of condensation along the linear nucleus. I 
looked at it myself on January 30th, and although it appeared 

as a mere speck, in comparison with its former grandeur, yet it 
had a tolerably bright appearance, and the elongated nucleus 

could be seen on the preceding side of the nebulous looking 
mass. I saw it agaiii on Feb. 6th and 2,6th, when I found 
it had very materially diminished in brightness. In the very 
centre was a bright point of light, looking something like a 
new point of condensation, but upon close examination it 
proved to be merely a fixed star. With respect to the wonder- 
ful disruption of the nucleus, it may be as well to mention 
that such an occurrence is by no means unprecedented. 
Hevelius and other astronomers mention, among their astro- 
nomical aphorisms, that the nuclei of comets are sometimes 
'' divided into two, three, or more parts of divers magnitudes, 
crassitudes, density and colour, that they sensibly increase and 
decrease, and those which suddenly increase are of shortest 
duration, and vice-versa; that they sometimes consist of very 



22 The Transit op Venus, 1882. 

which public attention was then actively directed, and some 
valuable data acquired, particularly on the latter occasion ; 
but upon the whole nothing very definite as to the mean 
distance of the earth from the Sun could be decided upon 
after examination of the many careful observations of the 
earlier transit which had been taken throughout the globe. 
As the result, however, of a somewhat exhaustive discussion, 
by the great astronomer Encke, of the somewhat discordant 
observations of 1769, the distance of the Sun was considered, 
up to a comparatively recent period, to be 95,298,260 miles. 
The next transit did not occur until the year 1874, when, 
although it was observed by many skilful astronomers, yet 
the mean results of all their observations have a tendency to 
show that, notwithstanding the utmost care had been 
exercised, even in the most minute particulars, for observing 
the phenomenon, yet their value for the true determination of 
the Sun^s distance became very questionable, and led to much 
disappointment among those who had taken so much trouble 
in the preparation, completion, and reduction, of their various 
observations. 

After another interval of eight years the transit of 1882 
has lately occurred, for the observation of which the most 
elaborate and complicated ^^ Instructions " had been issued 
both to professional and amateur observers throughout the 
world, more especially by the American Congress, who 
most liberally supplied them to all who were supposed to take 
an interest in the important event. As the majority of ob- 
servers in this country were most unfortunately prevented by 
unfavourable weather, from witnessing any portion of the 
transit, it becomes, I think, the duty of those who were more 



The Transit op Venus, i88a. 23 

favoured to place on record their several observations, how- 
ever trifling and unimportant they may appear. 

On account chiefly of the considerable elevation of my 
observatorj' above the sea level (825 feet), which placed me 
above the lower layer of cloud, I was enabled to see a con- 
siderable portion of the transit, particularly during the time 
when the following {i,e,, the eastern) semi-diameter of the 
planet was entering upon the Sun^s disc. My remarks will 
therefore refer to the important few minutes which were sub- 
sequent to external, but preceded internal, contact of the 
limbs of Venus and the Sun. 

The following is a summary of my observations at Crow- 
borough, the greater part of which is a reprint from '* The 
Monthly Notices of the Royal Astronomical Society " of my 
letter to them on Dec. 7th : — 

Observations of the Transit of Venus ^ 1882, December 6, 

made at Crowborough, Sussex. 

The morning of Dec. 6 looked as unpromising for seeing 
the very interesting phenomenon which was about to happen 
as could well be imagined. Tlie temperature at 9 a.m. was 
only 31°; the barometer was low and the wind N. Added 
to this the sky was so densely overcast that one of Crookes's 
radiometers scarcely performed one revolution per minute, and 
slight showers of hail, sleet, and snow were falling at intervals 
until noon. The first gleam of sunshine appeared at ih. 40m., 
but two minutes afterwards the Sun was again obscured till 
ih. 55m. by a large mass of cumulus cloud lying above some 
drifting scud. The Sun was obscured till 2h. I am., when, 
through a break in this cloud, the Sun shone out with Venu^ 



04 The Transit op Venus, 1882. 

having passed half her diameter upon his disk. A minute 
afterwards the sun was again obscured till ah. i6m., when 
the heavier clouds passed away, and I had no further serious 
interruption from them during the remainder of the after- 
noon. On account of my elevation above sea-level (825 feet) 
I was favoured by being situated just above some drifting 
scud, a dense stratum of which wa^ passing below me ; and 
when, now and then, a thin portion of this passed before the 
Sun, it rather tended to improve the definition than other- 
wise. From 2h. 16m., therefore, I watched very attentively 
the near approach of internal contact. At 2h. 17m. I first 
noticed the visibility of that portion of the planet still outside 
the Sun's disk, and which appeared to be illuminated by a 
brilliant line of light, which most distinctly marked the limb 
of that portion of the planet, and which was doubtless pro- 
duced by the refraction of sunlight passing through the 
planet's atmosphere. 

The beautiful effect of the Sun lighting up the atmosphere 
of Venus I have endeavoured to represent in the accompany- 
ing sketch. {See Fig, 3). In some drawings of this pheno- 
menon which I have lately seen, the light was less sharply 
marked over the planet's limb, but diffused somewhat more 
over the planet's surface. The sketch, however, represents 
accurately what was seen by me, and corresponds with an 
observation made by Vice-Admiral Sir Erasmus Ommanney 
at Luxor, Egypt, at egress, during the transit of 1874. 

At 2h. 22m. 7s. I noticed that the planet's disk became 
slightly distorted, and then apparently elongated upon the 
Sun^s limb, so that I became somewhat perplexed how I 
should determine the instant of contact. This feature con- 



Fio. 3. 



THE PLANET VENUS ADVANCING 
UPON THE SUN, 

i.t., Passing between the Sun and the Earth. 



Flo. 4. 



THE LIMB, OR EDGE, OF THE 

PLANET JUST PASSING THAT 

OF THE SUN. 



10^ 



.1* 



- r 



1' 



't ' > J. .. i 



. . » i 



V ! 



r 



The Transit op Venus, i88ij. 25 

tinued till 2h. 22m. 15s., when I observed the following. This 
shadow, or ligament, or whatever it was, suddenly left the 
Sun's limb in something less than a second of time, and 
gathering up towards the planet was no longer visible. It 
did not lengthen itself, or become narrower, or form a black 
drop towards the Sun, but merely disappeared, as I have 
before said, close to the planet. When this had happened I 
found that internal contact was over, and that there was a 
clear line of separation between the two limbs. I consider, 
therefore, that the above time of ah. 32m. 15s. was late, and 
that actual contact had been over 3s. or 4s., which would 
bring the time of contact to corresp(>nd very closely indeed 
with the theoretical time of contact for my Observatory, 
which was kindly sent me by Dr. Hind on the 3rd inst. — 
viz., .2h. 22m. IIS. The following is a sketch of the 
phenomenon about 2h. 22m. 12s. {See Fig. 4.) 

I next directed my attention to the general appearance of 
Venus, now fully upon the Sun's disk, and I at once per- 
ceived that a halo of yellowish light surrounded her — it was 
not a rivgy as in the case of Mercury, but a very diffused 
light, and constantly varying in breadth — now here, now 
there. As the planet advanced, this halo became much 
fainter, until at 3 p.m. it was no longer visible. There was 
no appearance of a satellite. The planet's surface was 
uniformly black, without the slightest speck of light visible 
anywhere upon it. At 3h. 30m. I went to my upper Obser- 
vatory with the intention of watching the phenomenon down 
to the horizon with my 3-in. Wray telescope. When within 
five degrees of the visible horizon the planet became decidedly 
elongated, and just at last almost linear. It was a splendid 



26 The Transit op Vends, 1882. 

sunset — the Sun, shorn of rays and of a beautiful carmine 
colour, lit up some surrounding clouds with many gradations 
of the same tint, the effect of which was visible some time 
after the disappearance of the magnificent orb with its planet 
behind a large mass of cumulo-stratus cloud lying over the 
sea. It was a sight not to be forgotten by those who 
witnessed it. I did not take any micrometrical measures or 
photographs, having quite decided upon merely watching 
what might happen, and recording what was noteworthy. 



The Transit of Venus, 1882. ^7 

HAS VENUS A SATELLITE? 

A special point of interest to be determined on the occasion 
of a transit of Venus is whether, when the planet is on the 
solar disc, any attendant satellite can be detected. Those 
eminent astronomers, Cassini in the 17th, Short and 
Montaign in the i8th centuries, published accounts of 
their having seen a satellite. These were collected and 
inserted in the fourth number of " The Mathematical 
Magazine and Philosophical Repository,^' a small monthly 
journal published in the year 1761. The object in printing 
these observations at that particular time was doubtless in 
anticipation of the transit about to occur, and which would 
afford the best possible opportunity for testing the existence 
of any satellite. 

As I have reasons for supposing that this little publica- 
tion is very scarce, I have thought it worth while to reprint 
the whole of their communications upon the subject, if only 
for the purpose of repeating the record of what appears to be 
of some interest in the science of astronomy, and useful for 
reference. 

To the Directors of the Mathematical Magazine. 

Gentlemen, 

Mr. Baudouin, Counsellor of the Grand Council 
at Paris, having done me the honour to transmit to me 
copies of two Memoirs written by himself concerning some 
new observations on a Satellite of the Planet Venus, lately 
read at the Royal Academy of Sciences, I send you a succinct 
account of them to be inserted, if you think proper, in your 
Magazine, that the lovers of astronomy may be rightly 



28 The Transit op Vbnos, 1882. 

informed as to the particulars of this most curious and 

interesting Phaenomenon. 

Yours, etc., 

J. Bevis. 
June 24, 1761. 

In the first memoir, the author says that, having fitted up 
a 25 foot telescope for observing the transit of Venus over 
the sun the 6th of the ensuing June, and also to try if he 
could find out her satellite in the months of April and May, 
some accounts of which he had met with in the printed 
memoirs of the Academy, he communicated his project to 
the secretary of the society at Limoges, who thereupon con- 
ferred with M. Montaign, one of the members, and engaged 
him to second M. Baudouin in his enterprize. M. Montaign, 
though at first a little incredulous, was most agreeably sur- 
prised to perceive with a nine foot telescope, on the 3rd of 
May, at half an hour after 9 in the evening, a fine slender 
crescent about 20' distant from Venus, its diameter being 
about one-fourth of that of the principal Planet. 

A line drawn from Venus to the satellite, made below 
Venus, with the vertical, an angle of about 20 degrees to- 
wards the south. 

Though M. Montaign repeated his observation again and 
again, yet he remained in some doubt if the phaenomenon 
might not be a small fixed star. 

The next day. May 4, at the same hour, he perceived the 
same thing again, but about half a minute or a minute more 
remote from Venus, and now making with the vertical an 
angle about 10 degrees under her, on the north side ; so that 
the satellite seemed to have described an arch of about 30 



The Transit of Venus, 1882. 29 

degrees, of which Venus was the centre, and the radius 
about 30 minutes. Such a change of position could not be 
attributed to Venus, for in the past 24 hours her motion in 
longitude was about ao'. If then the phaenomenon had been 
a fixed star, it would not have been found after a day, at 
nearly the same distance from Venus, but at about twice the 
former distance. 

A fog hindered the observer from distinguishing the satel- 
lite on the 4th, though he could perceive the planet through 
it ; nor could he satisfy his impatience for the same reason 
before the 7th of May, when again at half-hour after nine 
in the evening he saw the satellite a third time, but above 
Venus on the north side, and 2,5 or a6 minutes from her on 
a line which made an angle of about 45 degrees with the 
vertical on the right hand. 

The light of the satellite was always feeble, and its shape 
constantly that of a crescent, and it was equally visible 
whether Venus were within the field of the telescope, or 
without it. 

The telescope magnified between 40 and 50 times. 
Before inferring any conclusions from these observations, 
M. Baudouin gives a short recital of what Messrs. Cassini 
and Short have written on the like phenomenon. 

M. J. D. Cassini, in his tract concerning the Discovery of 
the Zodiacal Light, says : — 

^^ On the 35th of January (N.S.), 167a, from 6h. 5a' in 
" the morning to 7h. 2' I saw a small luminous appearance, 
which imitated the phasis of Venus, and then the bright- 
ness of the twilight effaced it. Venus at this time put 
on the shape of a crescent, and the phaenomenon, which 






30 The Transit op Venus, i88a. 



a 






was about a quarter of her diameter, looked like a crescent 
'^ likewise. Its distance from the southern cusp of Venus, 
'^ westward, was equal to one of her diameters. 

*' The 8th of September, 1686, a quarter after four in the 
*' morning, lookiug at Venus with a 34 foot telescope, I per- 
*' ceived at about three-fifths of her diameter, eastward, an 
'' ill-defined light seeming to imitate the phasis of Venus, 
^' which had then lost its rotundity on the west side. The 
'^ diameter of the phaenomenon was about the 4th of that of 
" Venus. 

*' I observed it with close attention for a quarter of an 
'^ hour, but having desisted four or five minutes, I could see 
^' it no more, the daylight being then far advanced. 

In these two observations I suspected that the said 
phaenomenon might be a satellite of Venus, of a consistence 
" not very well adapted for reflecting the light of the Sun, and 
*' bearing nearly the same proportion to Venus as the moon 
'' to the earth, being at the same distance from the Sun and 
"the earth as Venus, whose phasis it resembled. 

" But with all my endeavours, after these two observations 
'* to complete a discovery of so much moment^ though fre- 
'^ quently repeated at different times, I never could see it 
*' more, for which reason I suspend my opinion concerning 
" this phenomenon ; which, if it shall happen to return more 
*' frequently, there will be the aforesaid two epochs to be 
*' compared with other observations in order to fix the rules 
*' of its return." 

About 50 years after this, when, says the author^ everyone 
had given up the belief of the existence of such a satellite, 
Mr. Short happening to look at Venus with a reflecting 









The Transit of Venus, 1882. 31 

telescope of only 16*5 inches focal length, saw again the same 
phaenomenon. His observation is related in the '* Philo- 
sophical Transactions," Numb. 459 ; and also in the 
'^ History of the Royal Academy of Sciences '* for 1741. Mr. 
Short^s account runs thus : — 

The a3rd of October (O.S.), 1740, at sunrise directing a 
reflecting telescope of 16*5 inches focus (with an apparatus 
to follow the diurnal motion) towards Venus, I perceived a 
'^ small star pretty nigh her ; upon which I took another 
" telescope of the same focal length, which magnified about 
50 or 60 times, and which was fitted with a micrometer, in 
order to measure its distance from Venus, which I found to 
'^ be about ten minutes. 

" Finding Venus very distinct, and frequently the air very 
^* clear, I put on a magnifying power of 240 times, and to my 
'^ great surprise found this star to have the same phasis with 
'^ Venus. 

" I tried another magnifying power of 140 times, and even 
^* then found the star under the same phasis. Its diameter 
*' seemed about a third, or somewhat less, of the diameter of 
*' Venus ; its light was not so bright or vivid, but exceeding 
'' sharp and well defined. A line passing through the centre 
^^ of Venus and it, made an angle with the equator of about 
18 or ao degrees. I saw it for the space of an hour several 
times that morning, but the light of the Sun increasing I 
lost it altogether about a quarter of an hour after eight. I 
^^ have looked for it every clear morning since, but never had 
'* the good fortune to see it again/^ 

Nothing surely, continues M. Baudouin, could be more 
decisive in favour of M. Cassini^s discovery than the observa- 



€< 



32 The Transit op Vknus, 1882. 

tion of this illustrious Englishman^ wbo^ setting himself above 
all national hatred, thus renders a solemn testimony to 
France. How far such an observation is to be relied upon, 
the celebrated name of Short, the first among opticians, and 
among astronomers the thoroughest judge and the best con- 
structor of telescopes, must undeniably evince. Yet, after all, 
when the same Mr. Short, even with his la foot reflector, the 
largest and most powerful that has yet been made, has so 
often sought in vain, for what he only once saw by chance 
with a common reflector, his observation is to be considered 
as no less solitary and fruitless than that of M. Cassini. To 
me it seems at least probable that this satellite has accidental 
or periodical returns of light, which at certain times render it 
visible, though it be invisible at others, of which there is a 
like example in the vicissitudes of the fifth satellite of Saturn, 
which sometimes looks bigger than the third, and at certain 
seasons decreases both in size and splendour till it quite 
vanishes, which happens chiefly when it is in the eastern part 
of its orbit in respect to Saturn. 

M. Montaign having no micrometer fitted to his telescope 
his measurements were made only by guess, and a knowledge 
of the extent of the field of the telescope ; consequently no very 
great degree of accuracy can be expected from the results,* and 
I shall not mention them but with much caution. Thus, 
though the orbit appears to me eccentric, I shall suppose it 
circular, being unable to prove by how many minutes the two 
axes differ. 

Figure 5 represents M. Montaign's three (first) observa- 
tions. V is the planet Venus, whose crescent inclined towards 
the north, extends its cusps upwards. Z N is the vertical. 



Via. 5. 




^^ 



The Transit of Venus, i88a. 33 

E C the ecliptic or a parallel to it, which at that time formed 
an angle of 45 degrees with the vertical. The numbers — 
3, 4, 7 show the distances and positions of the little cres- 
cent; the distance V3 being 20 minutes, V4 ill minutes, 
and V 7 about 26 minutes. 

The figure shows that the observations of the 3 and 7 
would have been diametrically opposite, if the satellite had 
proceeded 25 degrees further about the point V in the last 
observation ; so that in four days it run through 155°, sup- 
posing its apparent orbit circular (from which we shall see 
that it differs not much) we may say, 155° : 96h : : 360® : to a 
fourth term, which gives nine days seven hours for the dura- 
tion of an entire synodic revolution of the satellite about its 
primary, or its return to the same position, with respect to 
Venus seen from the earth at that time. Supposing, then, 
the orbit of its satellite to be circular, its apparent radius was 
about 23 minutes. 

The distance of Venus from the Sun was then to that of 
the Sun from the earth, as 100 to 215. So that when Venus 
shall be at her mean distance with respect to us, or at the 
same distance as the Sun, the orbit whose apparent radius was 
to us 23 minutes, will appear to be no more than 1 1 minutes. 
On the contrar)', when Venus comes to pass over the Sun, the 
satellite's greatest elongation will amount to 37 minutes. Now 
the diameter of Venus seen from the earth at that time will be 
I J minute, and so the satellite's distance with respect to 
Venus, or the radius of its orbit, is about 60 semi-diameters 
of its planet, as the moon's distance from the earth is 60 times 
the earth's semi-diameter. 

The distances of the 3, 4, and 7 being nearly equal, it 

c 



34 The Transit of Venus, i88a. 

follows that the position of this orbit is nearly perpendicular 
to the ecliptic : it also follows from this equality of apparent 
distances that the orbit of the satellite was perpendicular to 
our visual ray. But the ray by which Venus was at that 
time observed extended to about two signs and zz degrees of 
longitude, so that the nodes of the satellite fall about the 22nd 
degree of Virgo and Pisces. 

From the position of the node then observed it follows that 
when Venus, seen from the earth is 2a® of Virgo, the orbit of 
the satellite will pass through our eye, and we shall then see 
it describing a right line perpendicular to the ecliptic, which 
passes through the centre of Venus ; and the satellite every 
revolution will be seen to transit the disk of Venus, and after- 
wards to be hid behind that planet. Such was its position 
nearly at the times of both M. Cassini's observations, and so 
will the orbit be disposed about the end of next October, the 
most favourable time that can be chosen to determine with 
certainty the place of this satellite's node. 

Supposing this satellite's synodic period to be exactly 9 
hours and 7 minutes, it should, after that interval, be again 
perpendicularly over the ecliptic at its greatest digression, as 
it was observed the 7th of May. This will happen the 26th 
of May at noon, and the 4th of June at 7 in the evening, 
whence it further follows that on the 6th of June at 9 in 
the morning, at Venus's egress from the Sun, the satellite 
will have passed this digression by 28 hours, or 31 degrees, 
so that it may be seen in the Sun. 

Let S be the Sun's centre; A the position of Venus on the 
Sun; BZ C D FN the orbit of the satellite, at that time 
nearly circular {See Fig, 6) to us; B the point of the circle 



Fig. 6. 




The Transit of Venus, i88a. 35 

of latitude cut by the orbit. Take an arc B C of 61 degrees, 
and the perpendicular C L will represent the track over the 
Sun, supposing the position of the point C to have been 
exactly determined. The difference of latitude A L in this 
case is no more than 18 minutes; the distance A G of Venus 
from the Sun's northern limb will be 26m., according to the 
calculation in the ^* Connoissance de Tems" for 1761. On 
this supposition the satellite should enter the Sun about 10 
o'clock, and describe a chord north of the centre equal to that 
of Venus south of it 

M. Baudouin concludes his first memoir by insisting that 
the satellite of Venus no longer remains a matter of un- 
certainty; that though himself sought it in vain the 17th of 
May, yet the twilight and moonshine were more than suffi- 
cient to defeat his purpose, and to continue to do so till the 
month of July, when he hopes for success, though it be 
possible enough that other circumstances, of which we know 
not the cause, may keep it much longer invisible. 

The second memoir concerns a fourth observation of the 
satellite of Venus made by the same M. Montaign at 
Limoges. 

It had been, it seems, insinuated by some of the members 
of the Academy that what the observer at Limoges took for a 
satellite was probably either a fixed star or some fallacious 
light formed on the glasses of the telescope. 

Out of respect, therefore, to those illustrious astronomers, 
M. Baudouin's ambition led him to attempt the removal of 
their doubts. He therefore gives them to understand that M. 
Montaign, resolving to avail himself of the only opportunity 
left him before the too great increase of the moon and the 



36 The Transit op Venus, i88a. 

twilight, did, on the 1 ith of May, at 9 in the evening, for the 
fourth time, obtain a sight of the little star near Venus, 
which was then at the same distance from her as on the 7th, 
namely, about 25 minutes, making, with the vertical passing 
through Venus, an angle of 45 degrees towards the south, and 
above the primary planet. 

The day of this last observation, says our author, Venus 
having passed the meridian at ah. 15m., was, at 9 o'clock, 
distant from it 6Jh., having 2yi degrees north declination. 
The vertical made, with the circle of declination passing 
through Venus, an angle of 4a degrees, but that planet 
having as. aad. of longitude, the circle of latitude was then 
3 degrees above the circle of declination on the north side ; 
wherefore the parallel to the ecliptic made an angle of 45 
degrees with the vertical, which gave me to understand that 
at that time it passed its descending node. And this ob- 
servation confirms what I offered to the Academy in my first 
memoir, touching the inclination, the nodes, and the distance 
of the satellite. In a word, it appeared at the same distance 
as on the 7th, but further advanced by about 90 degrees ; 
therefore, during this month of May, its orbit is nearly per- 
pendicular to our eye, and cuts the ecliptic on a line which 
crosses at right angles the line which we see Venus, namely, 
at IIS. aad., and the point opposite thereto, or in the 22 
degrees of Virgo and Pisces. 

Venus being almost stationary this month, it is not at all 
strange that the orbit is constantly in the same position ; 
and supposing the observations to be more exact than they 
really are, being made without a micrometer, it is certain 
from the earth's position, and the parallelism of the lines by 



The Transit op Venus, 1883. 37 

which we see Venus from the beginning of the month, that 
the orbit of the satellite is always, is ever, presented to us in 
the same manner; that is constantly perpendicular to our 
visual ray, and ever disposed circularly round Venus, 

It further follows from this fourth observation, as from 
the preceding ones, that the orbit of the satellite is perpen- 
dicular to the ecliptic ; for if it were inclined to it, our eye 
ever posited in the plane of that great circle could not at any 
time view the orbit of the satellite under a circular form ; but 
would always see it as an ellipse whose larger axe would be 
to its lesser in the ratio of the radius to the sine of the 
obliquity of the orbit to the ecliptic. 

For obtaining as exactly as may be the satellite's distance 
from Venus in diameters of the planet, M. Baudouin supposes, 
with M. le Monnier, that Venus's apparent diameter at her 
least distance from the earth is ifm., whence he computes 
her distance from the earth in the observations of the 7th and 
the iJth, and finds her diameter then 53s.; whence he 
infers that the radius of the satellite's orbit is about 50 of 
the radii of Venus. 

He finds that the satellite's revolution is slower than 
according to the three first observations, and rests it at 12 
days. 

He observes that because Venus is stationary in the month 
of May, the satellite's synodic revolution diflFers not sensibly 
from its periodic one; a consideration otherwise naturally 
obvious, in consequence of the perpendicular position of its 
orbit, whereby the synodic revolution can never diflFer from the 
periodic, even though Venus runs through 90 degrees in her 
orbit in the space of la days. The satellite always traverses 



38 The Transit op Vknus, 1882. 

her orbit at the same point, and at the same time, as if Venus 
had remained unmovable ; and it is the same as to its synodic 
revolution in respect of the earth. 

In consequence of this longer period, he finds the passage 
of the satellite over the Sun far more doubtful. In effect, 
the satellite, having passed its node at M in the last figure^ 
on the nth of May, at 9 in the evening, should be there 
again on the 4th of June at the same time ; and the 5th, in 
the morning, it should have passed the node by 45 degrees, 
and be at O ; so that following Venus, and describing the line 

R N, it would pass 25m. more south, and consequently 
above aom. distance from the Sun's southern limb, 

M. Baudouin takes notice that in the observation of the 

1 ith, M. Montaign saw a fixed star on one side of the satellite 
and Venus, and that this star was the northernmost of the 
four unformed ones under the feet of Auriga ; so that he has 
a sure point with which to compare the position of the planet 
and satellite. 

He concludes with this remark : that the most important 
benefit which astronomy can derive from a discovery of the 
distance and periodic time of a satellite of Venus, will be the 
knowledge of the quantity of matter in the primary, and 
hence of the force with which this planet works upon the 
earth, thereby producing different and very considerable 
effects, such as the diminution of the obliquity of the 
ecliptic, and the alteration of latitude in the fixed stars^ etc. 

Certificate of the Academy, extracted from the Register of 

the 30th of May. 

We having examined, by order of the Academy, the remarks 
of M. Baudouin on a new observation of the satellite of 



The Transit op Venus, i88a, 39 

Venus, made at Limoges, the nth of May, by M. Montaign. 
This fourth observation, of great importance for the theory 
of the satellite, has shown that its revolution must be longer 
than appeared by the three first observations. M. Baudouin 
believes it may be fixed at 1 2 days ; as to its distance, it 
appears to him to be 50 semi-diameters of Venus ; whence 
he infers that the mass of Venus is equal to that of the earth. 
This mass of Venus is a most essential element to astronomy, 
as it enters into many computations, and produces diflerent 
phenomena. But though M. Baudouin expects a great 
many more observations, in order to pronounce more 
decisively from them, yet we consider this second memoir as 
essentially connected with the first, and think it well worthy 
to be printed. Done at Paris, in the Assembly of the Royal 
Academy of Sciences, the 30th of May, 1761. 

Signed L'Abbe Db La Caille, 

De la Lande. 

I certify that this present extract is conformable to the 
original, and to the judgment of the Academy. Paris, this 
30th of May, 1761. 

Signed Grandjean de Fouchy. 

Perpetual Secretary of the Royal Academy of Sciences. 

After considering the account thus given by these three 
astronomers, all of whom hold an important position in 
astronomical science, it appears somewhat difficult to ignore, 
absolutely, the correctness of their observations. It has 
been stated, as a fact, that in consequence of the imperfection 
of the eye-pieces which were applied to some of the earlier 
telescopes, especially to those of long focal length, they not 



40 .The Transit op Venus, 1882. 

infrequently gave a secondary image of the object under 
examination. We are informed that this supposed satellite 
of Venus was seen on very few occasions ; but if the image 
seen in the telescope was caused by reflection from the 
primary^ how comes it that this reflection was not always 
seen whenever the telescope was directed to the planet ? We 
are told that observers repeatedly searched for the satellite 
with, probably, the same telescopes, but we do not hear that 
they saw this supposed phantom on every occasion, but are 
distinctly told, on the contrary, that they did not. 

Besides the preceding accounts of the visibility of the 
satellite, I will proceed to mention the following records and 
opinions respecting it, which certainly have a tendency to 
support the theory of its existence. 

On March 4, 1764, Rodkier, of Copenhagen, with a tele- 
scope 38 feet long, saw Venus with a satellite. His friend 
Horrebow, a Professor of Astronomy, thought he saw the 
satellite on March 10th and nth, and, apparently suspecting 
the possibility of an optical illusion, took especial pains to 
counteract the same. Montharon also saw a satellite on 
March • 28 and 29, but at each observation in a different 
position, a fact which strongly opposes the reflection theory. 
During the transit of 1761, Scheuten felt satisfied that he 
saw Venus was accompanied by a satellite. I will conclude 
my remarks upon this subject with the opinions expressed 
by the late Admiral Smyth in the " Cycle,'' vol. i., page 109. 
'* The question whether Venus has a satellite or not has 
been warmly and widely contested ; no such attendant seems 
to have been undeniably detected, but to the present moment 
it cannot be demonstrated that it is not in existence. The 



The Transit op Venus, 1882. 41 

satellite of an inferior planet, especially if it were very small, 
would be extremely difficult to find, for when the primary is 
nearest to the earth, and circumstances are most favourable 
for its discovery in other respects, the dark side would be 
turned towards us. 

"Besides Baudouin, Rodkier, and other astronomers, 
Cassini and Short, two exact observers, were positive as to 
having perceived a satellite, and, from the published details, 
Lambert has given a very consistent theory of its action. 
But it has been pronounced, and that rather dogmatically, 
that the observers must have been deceived by stray light, 
ghosts, false images, or other optical illusions of imperfect 
telescopes ; and that opinion is founded upon the fact of no 
secondary body being seen when Venus traversed the solar 
disc. Yet this, although a strong point, is not admitted by 
Lambert, and even if it were, would be scarcely conclusive, 
for in different countries, and with different eyes and means, 
that optical illusion must have been truly marvellous which 
could pervade the minutely detailed observations of Cassini 
in 167a and 1686, of Short in 1740, and Montaignin 1761. 
Sir David Brewster says ' That Mr. Wargenten had in his 
possession a good achromatic telescope which always showed 
Venus with such a satellite, and the deception was dis- 
covered by turning the telescope about its axis.^ This, how- 
ever^ must be a mere pleasantry, for it is impossible that 
the accurate, observers cited could have been deceived through 
so gross a neglect. Cassini employed a 34 foot refractor at 
epochs with fourteen years between them, and Short used 
two reflectors, to the second of which he applied three 
different eye-pieces, magnifying 60, 140, and 240 times. The 

D 



43 Tbb Trahsit op Venus, 1882. 

contested satellite is, perhaps, extremely minute, while some 
parts of its body may be less capable of reflecting light than 
others, and when the splendour of its primary, and our incon- 
venient station for watching it are considered, it must be 
conceded that, however slight the hope may be, the search 
ought not to be relinquished." 



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