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ately detected by its disc, under of the lowest magnitude above
a high magnifying power.

specified, would suffice to assure
Such, briefly, is the well-known the observer of the presence of an
history of the discovery of those object in a particular position on
planets of our system which re one evening which did not occupy
quired the aid of optical resources that position on a preceding. M.
and of persevering search among Hencke, while examining a portion
the stars for the detection of their of the heavens in the fourth hour
existence; and it is interesting to of R.A., on December 8, was im-
find that we are indebted for our mediately aware of the presence,
knowledge of Astræa to a similar directly between two stars of the
sagacity and perseverance. The 9.10th magnitude, marked on the
discoverer, M. Hencke, of Driessen Berlin maps, and denoted by the
in Prussia, is a gentleman who, positions.
at one period of his life, was em-
ployed in the post-office of that

R. A.............4h 18m 45°

N.P.D. ......77° 18 1"
town, but who, being gifted with
a taste for astronomical pursuits, And R. A.
has, for the last fifteen years, been

N.P.D" "}

......... 4h 20m 20°
rendering himself familiar with the
general features of the heavens, of a star of the 9th magnitude, not
for the express purpose of dis- marked on the maps ; and, from
covering such a body as has now

his familiarity with this part of the
rewarded his exertions. The cir-

beavens, he felt assured that the cumstances which attended the dis

star did not previously exist there. covery of the other four asteroids He wrote immediately to Professor rendered it, antecedently,

Encke, and soon afterwards to tremely probable that others vet

Professor Schumacher (the letter remained to be detected ; and the

to Schumacher was received by difficulty lay in conducting a search him December 13), announcing his of such a nature. The body to be suspicions of the discovery of a discovered would be probably of a

new planet, and giving the position brightness equivalent to a star of of the star in question for the time from the 8th to the 10th magni

of his observation, viz.-
tude, and the only sensible circum.

Dec. 8, 8h Berlin Mean Time.
stance in which it would differ
from the star would be its motion.

R.A........

= 65 25
But the motion of a body can be N.P.D.

77 19
detected only by comparisons be-
tween its situations on different Professor Encke and Professor
days; and there would be nothing Schumacher immediately made
to direct the choice of the objects public M. Hencke's communica-
to be tried amongst the hundreds tion; the new planet immediately
that one sweep of the telescope became the focus of observation to
would present to the observer. all the astronomers of Europe and
Nothing, then, it is evident, but a America, who published the results
complete familiarity with the part of their investigation, which, as is
of the heavens under review, and a to be expected, all differ somewhat
knowledge of the relative positions from each other, although in a very
of all the stars in it, to the limits slight degree. Those of Encke, as

ex

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ance ; and in that spot, and with 458 ANNUAL REGISTER, 1846. reported by Professor Schumacher, the presentation of such histories. are appended. It was unanimously Yet it is conceivable that events agreed to give the name of Astræa may occur in which this rule ought to the new orb.

to be relaxed ; and such, I am Elements of Encke, communi- persuaded, are the circumstances cated by Professor Schumacher, attending the discovery of the 1845, December 25,

planet exterior to Uranus. In the

whole history of astronomy-I had , }

almost said in the whole history of

89 32 12.1 tude, 1846, Jan. 0 On

science there is nothing comparPeribelion................

214 53 7.0

able to this. Node

The history of the 119 44 37.5 Inclination

7 42 8.4

discoveries of new planets in the Eccentricity

0.207993 latter part of the last century, Q = 12° 0' 17.1

and in the present century, offers Log. semi-axis major 0.42144

nothing analogous to it. Uranus, Daily motion

8274.65 Time of revolution = 1565 days.

Ceres, and Pallas, were discovered

in the course of researches which Co-ordinates and constants for did not contemplate the possible the equator (v = true anomaly) : - discovery of planets. Juno and

Vesta were discovered in following x = ra sin (A + y); log. a = 9.99704;

up a series of observations sugA 305° 6' 351 y = rb sin (B + »); log. b 9,97440;

gested by a theory which, fruitful B 217° 29' 5"

as it has been, we may almost z = rcsin (C + »); log. c = 9.54802; venture to call fanciful.

Astræa C 197° 1' 46"

was found in the course of a wellII. Account of some circum- conducted re-examination of the stances historically connected with heavens, apparently contemplating the discovery of the planet exterior the discovery of a new planet as to Uranus. (Read by the Astro- only one of many possible results. nomer Royal.)

But the motions of Uranus, exa

mined by philosophers who were It has not been usual to admit fully impressed with the univerinto the memoirs of this society sality of the law of gravitation, mere historical statements of cir- have long exhibited the effects of cumstances which have occurred in

some disturbing body: mathemaour own times. I am not aware ticians have at length ventured that this is a matter of positive on the task of ascertaining where regulation : it is, I believe, merely such a body could be ; they have a rule of practice, of which the pointed out that the supposition of application in every particular in- a disturbing body moving in a cerstance has been determined by the tain orbit, precisely indicated by discretion of those officers of the them, would entirely explain the society with whom the arrange- observed disturbances of Uranus: ment of our memoirs has princi- they have expressed their convicpally rested,

And there can be tion, with a firmness which I must no doubt that the ordinary rule characterize as wonderful, that the must be a rule for the exclusion of disturbing planet would be found papers of this character, and that exactly in a certain spot, and if a positive regulation is to be senting exactly a certain appear. made, it must absolutely forbid

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Yet we

that appearance, the planet has adopted from the latter observabeen found. Nothing in the whole tions, leaving the discordances with history of astronomy can be com the former (amounting sometimes pared with this.

to three minutes of arc) for future The principal steps in the theo. explanation. retical investigations have been

The orbit thus adopted repremade by one individual, and the sented pretty well the observations published discovery of the planet made in the years immediately folwas necessarily made by one in- lowing the publication of the tables. dividual. To these persons the But in five or six years the dispublic attention has been princi- cordance again growing up became pally directed ; and well do they so great that it could not escape nodeserve the honours which they tice. A small error was shown by have received, and which they the Kremsmünster Observations of will continue to receive.

1825 and 1826: but, perhaps, I should do wrong if we considered am not in error in stating that the that these two persons alone are

discordance was first prominently to be regarded as the authors of exhibited in the Cambridge 06the discovery of this planet. I am servations, the publication of which confident that it will be found that from 1828 was conducted under the discovery is a consequence of my superintendence. what may properly be called a While still residing at Cammovement of the age; that it has bridge, I received from the Rev. been urged by the feeling of the T. J. Hussey (now Dr. Hussey) scientific world in general, and has

a letter, of which the following is been nearly perfected by the colla- an extract:teral, but independent labours, of various persons possessing the ta- Rev. T. J. Hussey to G. B. Airy. lents or powers best suited to the different parts of the researches.

“ Hayes, Kent, Without pretending to fix upon

17th November, 1834. a time when the conviction of the “ With M. Alexis Bouvard I irreconcilability of the motions of had some conversation upon a subUranus with the law of gravitation ject I had often meditated, which first fixed itself in the minds of will probably interest you, and some individuals, we may without your opinion may determine mine. hesitation date the general belief Having taken great pains last year in this irreconcilability from the with some observations of Uranus, publication of M. Alexis Bouvard's I was led to examine closely Tables of Uranus, in 1821. It Bouvard's tables of that planet. was fully shown, in the introduc- The apparently inexplicable distion to the tables, that, when every crepancies between the ancient correction for perturbation indicated modern observations sugby the best existing theories was gested to me the possibility of applied, it was still impossible to some disturbing body beyond reconcile the observations of Flam- Uranus, not taken into account steed, Lemonnier, Bradley, and because unknown. Subsequently, Mayer, with the orbit required by in conversation with Bouvard, I the observations made after 1781: inquired if the above might not and the elements of the orbit were be the case: his answer was, that,

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as might have been expected, it tion of the astronomers of Paris had occurred to him, and some was directed to Uranus. correspondence had taken place Although no allusion is made in between Hansen and himself re the last letter (M. E. Bouvard's) specting it. Hansen's opinion to the possible disturbing planet, was, that one disturbing body it would be wrong to suppose that would not satisfy the phenomena; there was no thought of it. In but that he conjectured there were fact, during the whole of these two planets beyond Uranus." efforts for reforming the tables

of Uranus, the donjinant thought My answer was in the following was, “ Is it possible to explain terms:

the motions of Uranus, without

admitting either a departure from G. B. Airy to Rev. T. J. Ilussey. the received law of attraction, [EXTRACT.]

or the existence of a disturbing

planet ?”. I know not how far Observatory, Cambridge, the extensive and accurate calcula23rd November, 1834.

tions of M. Eugène Bouvard may I have often thought of the have been used in the subsequent irregularity of Uranus, and since French calculations, but I have the receipt of your letter have no doubt whatever that the know. looked more carefully to it. It is ledge of the efforts of M. Bouvard, a puzzling subject, but I give it the confidence in the accuracy of as my opinion, without hesitation, his calculations, and the perception that it is not yet in such a state as of his failure to reconcile in a sato give the smallest hope of mak- tisfactory way the theory and the ing out the nature of any external observations, have tended greatly action on the planet. Flamsteed's to impress upon astronomers, both observations I reject (for the pre- French and English, the absolute sent) without ceremony : but the necessity of seeking some external two observations by Bradley and cause of disturbance. Mayer cannot be rejected. Thus Several months before the date the state of things is this——the of the last letter quoted, I had remean motion and other elements ceived the first intimation of those derived from the observations be- calculations which have led to a distween 1781 and 1825 give con tinct indication of the place where siderable errors in 1750, and give the disturbing planet ought to be nearly the same errors in 1834, sought. when the planet is at nearly the same part of its orbit. If the Professor Challis to G. B. Airy. mean motion had been determined by 1750 and 1834, this would

[EXTRACT.] have indicated nothing : but the

“ Cambridge Observatory, fact is, that the mean motions

February 13th, 1844. were determined (as I have said) A young friend of mine, Mr. independently. This does not look Adams, of St. John's College, is like irregular perturbation.' working at the theory of Uranus,

The astronomer royal then read and is desirous of obtaining errors a letter from M. Eugène Bouvard, of the tabular geocentric longitudes showing how vigorously the atten- of this planet, when near opposi

ner.

tion, in the years 1818-1826, with ments of your valuable time. His the factors for reducing them to er calculations are founded on the obrors of heliocentric longitude. Are servations you were so good as to your reductions of the planetary furnish him with some time ago; observations so far advanced that and from his character as a mayou could furnish these data ? and thematician, and his practice in is the request one which you have calculation, I should consider the any objection to comply with ? deductions from his premises to If Mr. Adams may be favoured be made in a trustworthy manin this respect, he is further de

If he should not have sirous of knowing, whether in the the good fortune to see you at calculation of the tabular errors Greenwich, he hopes to be alany alterations have been made lowed to write to you on this in Bouvard's Tables of Uranus, subject.” besides that of Jupiter's mass.” Professor Challis, in acknow- tober, 1845, Mr. Adams called at

On one of the last days of Ocledging the receipt of my answer,

the Royal Observatory, Greenwich, used the following expressions :

in my absence, and left the follow

ing important paper :Professor Challis to G. B. Airy. [EXTRACT.]

J. C. Adams, Esq., to G. B. Airy. “ Cambridge Observatory, February 16th, 1844.

“ According to my calculations, I am exceedingly obliged by the observed irregularities in the your sending so complete a se

motion of Uranus

may

be ries of tabular errors of Uranus.

counted for by supposing the ex* * The list you have sent istence of an exterior planet, the will give Mr. Adams the means of mass and orbit of which are as carrying on in the most effective follows: manner the inquiry in which he is engaged."

Mean Distance (assumed

nearly in accordance The next letter shows that Mr.

with Bode's law) 38.4 Adams had derived results from

Mean Sidereal Motion in
365. 25 days

1°30'.9 these errors.

Mean Longitude, lst of
October, 1845

323 34 Professor Challis to G. B. Airy. Longitude of Perihelion 315 55

Eccentricity

0.1610. “ Cambridge Observatory, Mass (that of the Sun September 22nd, 1815.

being unity)

0.0001656. “ My friend, Mr. Adams (who will probably deliver this note to

For the modern observations I have you), has completed his calculations used the method of normal places, respecting the perturbation of the taking the mean of the tabular orbit of Uranus by a supposed ul errors, as given by observations terior planet, and has arrived at near three consecutive oppositions, results which he would be glad to correspond with the mean of the to communicate to you personally, times; and the Greenwich observaif you could spare him à few mo tions have been used down to 1830 ,

ac

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