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received Piazzi's letters, the newly-discov- | been so long unsuccessful in their labours; ered planet had become lost to view, having and on the last day of the year the planet already approached that part of the heavens was detected by De Lach close to the place in which the sun was situated, and being assigned to it by the ephemeris of Gauss. thus lost to sight through the overpowering Thus, by a singular coincidence, the disbrilliancy of the solar light. covery of the new planet was the work of exactly one year. Detected on the evening of the first day of the present century, the stranger was finally admitted into the family of planets at the end of the first year of the century. On January 1st, 1802, the new planet was independently re-discovered by Olbers. The name Ceres was assigned to it.

Nothing remained for the present but to await the re-appearance of the missing orb. Six long months, however, were to elapse, and all this time the stranger would be speeding onward in an orbit of which so little was known, that it seemed all but hopeless that the place of the new planet should be guessed at after so long an interval. In the meantime a rough analysis was On a careful examination of the orbit of made of the stranger's path, and all agreed Ceres, a very satisfactory accordance with in the conclusion that Kepler's prediction the anticipations of astronomers was found had really been fulfilled, and that the new to result. On the supposition that the planet revolved in an orbit intermediate earth's distance from the orbit of Mercury between the orbits of Mars and Jupiter. is expressed by two, the distance of Ceres Not only was this found to be the case, but should have been eight: it is actually seven it was shown that the distance of the stran- and nine-tenths. ger corresponded very closely with the law which has been stated above.

In September, 1801, the search for the returning planet was commenced. But, as had been feared, it proved unfruitful. Again and again the keenest observers scrutinised those regions of the sky in which the stranger might be expected to appear, but no success rewarded their labours. "The world began to sneer," writes a modern astronomer, "at a science which could find a body in the heavens and then lose it for ever."

Observational astronomy had been tried and had failed the time had come to apply the powers of physical astronomy. The young astronomer, Gauss, already wellknown for his application of new modes of analysis to the computation of cometic orbits, was fired with the ambition of completing by means of computation the tracking process which Piazzi had pursued by actual observation, and had been compelled to leave unfinished.

The attempt was a bold one - almost as bold as that later effort which led to the discovery of distant Neptune. It was successful, however. The long process of calculation was finished a few days before the end of the year 1801; the calculated path of the planet on the celestial sphere was announced to the observers who had

But it was not long before some very anomalous features were observed in the relations presented by the new planet. In the first place, it was found to be a very minute object, not merely in comparison with the primary planets, but even when compared with their satellites. Sir W. Herschel estimated its diameter at only 161 miles; so that the surface of the new world (assuming this estimate to be correct) is considerably less than that of Great Britain. Then, again, the motion of the new planet is not of the orderly nature which is characteristic of the planetary system. It travels in a path which is considerably inclined to that plane in space near which all the other planets are observed to move.

While astronomers were speculating on these peculiarities, a new discovery was effected. The astronomer Olbers, during his search after Ceres, had familiarised himself with the aspect of all the telescopic stars which lie near the path followed by that planet. On the 28th of March, 1802, while examining a portion of this track region very near to the spot on which he had detected Ceres three months beforehe observed a small star of the seventh magnitude where no star, he felt sure, had been seen by him on any former occasion. Now there is nothing very uncommon in

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such an observation as this, because there the massive globe of a primary planet into are many stars which only shine out at in- fragments, and hurled these forth with suftervals. Olbers supposed the stranger to ficient energy to account for the anomalous be one of these fitful variables; but he motions of the recently discovered bodies. thought it well to re-examine the star, after He suggested the possibility that other an interval, in order to see whether it had fragments might be discovered; and he any perceptible motion. He found that it pointed out two parts of the heavens in was moving, and continuing his observa- which the search after such fragments would tions he established the fact that the stran- have the best chance of success. ger was a planet, on the very evening on which he had first discovered it.

The views of Olbers were quickly acted upon, and no very long time elapsed beIn exactly one month from the discovery fore the discovery of a third planet in one of this second planet, Gauss had calcu- of the very regions indicated by Olbers, lated its orbit. To the surprise of the as- seemed to confirm his fanciful theory. tronomical world, the stranger was found The new planet, which received the name to be quite as fitting a representative of of Juno, was detected by Harding, of LilienKepler's missing planet as Ceres had been thal, on September 2nd, 1804. It appears shown to be. Its mean distance is nearly to be smaller than either of the others, and the same as that of Ceres; and its dimen- revolves in an orbit of singular eccentricsions appear to be equally, or perhaps ity. more minute. But the orbit of the new planet presents one or two peculiarities. It is far more eccentric than that of Ceres, and it departs so widely from the mean plane of the planetary system, that Sir W. Herschel considered the term planet inapplicable to such a body. Hence arose the invention of the name asteroid, perhaps as ill-chosen a term as has ever been adopted by the scientific world.

The circumstance that two planets should be found revolving around the sun at nearly the same mean distance, attracted a great deal of attention among astronomers. In fact, we may look upon the discovery as one of the most remarkable that has ever been effected. For men began at once to see that there exists within the solar system a variety of structure of which they had hitherto had little conception. It is not saying too much to assert that a large proportion of the views at present held respecting the planetary system would have been scouted as bizarre and fanciful before the discovery of Pallas. For in astronomy, as in the other sciences, the range of the known limits man's conceptions respecting the unknown.

Confirmed in his views by this discovery, Olbers prosecuted the search after new fragments of his shattered planet with new energy. For two years and a half, however, he sought in vain. At length, on March 28th, 1807, his perseverance met with its reward, in the discovery of the largest known member of the asteroidal family. He was examining the northern wing of Virgo, when his attention was drawn to a brilliant star of the sixth magnitude in a neighbourhood with which his long-continued researches had made him intimately familiar. He had never before seen this star, and, therefore, felt convinced that it was a planet. It must be remembered that to a telescopist, sixth magnitude stars hold much the same position as first magnitude stars to the naked-eye observer. shine out in the field of view just as Arcturus, Aldeboran, or Sirius shine out among the lesser stars on the celestial vault. Therefore, a telescopist who has spent any time in examining a particular region of the heavens, would be as much struck by the discovery of a new sixth magnitude star, as any person familiar with the constellations would be if a new and brilliant star were to shine out in some well-known star-group.

They

So strange did the phenomena presented by the two new planets appear, that asA few hours' observation sufficed to place tronomers were led to suppose that possi- the planetary character of the star beyond a bly these bodies might be but the fragments doubt. Soon after, Olbers sent to Gauss of a large planet, which had once revolved, a series of observations for the determinabrilliant as Mars or Jupiter, between the tion of the new planet's path, and in two orbits of these planets. Men recalled the hours from the receipt of Olbers' communifanciful views of the ancient astronomer, cation, Gauss had completed the calculation who spoke of planets which had disap- -an achievement unexampled in the hispeared from the heavens. Olbers, the dis- tory of physical astronomy. The orbit of coverer of Pallas, was the first to give form the new planet was found to resemble that to the new theory. He supposed that of Ceres, Pallas, and Juno, but its distance some internal convulsion might have rent is somewhat smaller. It is the only aste

roid which has ever been visible to the naked eye, Schroeter being the only observer who has so seen it.

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four days later, M. Gasparis, of Naples, detected the same asteroid. Within a year, M. Gasparis had his revenge, however. Then for a long time the progress of dis- On the 18th of January, 1852, Mr. Hind covery ceased. It would seem that no fur- marked down in the ecliptical chart which ther search was made until about the year he was compiling, with the aid of Mr. Bish1830, when M. Hencke, an amateur astron- op's refractor, at the Regent's Park Obseromer of Driessen, in Germany, began a vatory, a star of the eleventh magnitude. careful survey of the zodiac belt. For fif- Cloudy weather prevented him from re-exteen years he continued to examine the amining this object for exactly two months. heavens without success. During all those On the evening of March 18th, he turned long years he was intent on the study of his telescope to the spot which had been ocstars which no unaided eye has ever seen. cupied by the small star; but the star had Laboriously he traced down their configura- vanished. Immediately he instituted tion, returning again and again to star- searching scrutiny for the missing object, group after star-group in hopes of detecting and would probably soon have detected it. the signs of change. But it was not until But, while the search was in progress, news the close of the year 1845, more than thirty- came of the discovery of an asteroid, in eight years after the discovery of Vesta, this particular region of the heavens, by M. that Hencke's unflinching perseverance met Gasparis. Professor Gauss was able to with its just reward. On the 8th of Decem- show that this object must on January 18th ber, he wrote to M. Encke, of the Observa- have occupied the exact place in which tory of Berlin, announcing the discovery of Hind had seen a telescopic star. In this a star in a certain position which he felt case, although Hind had not been able to sure had hitherto been untenanted. Encke detect the missing object, he would have examined the heavens in this neighbourhood been credited with the discovery of a new six days later, with the magnificent refrac-planet had he missed the star one day earlier. tor of the Berlin observatory, and quickly As it was, De Gasparis, having detected discovered a star which was not marked in the planet on the 17th of March (one day the observatory chart. As in former in- before Hind suspected its planetary nature), stances the planetary nature of the stranger, is entitled to the credit of the discovery. and the fact that it belongs to the same region of space already assigned to the other asteroids, were quickly established. Encke left the choice of a name with Hencke, who selected the name Astræa.

With the discovery of another planet by M. Hencke, in July, 1847, may be said to have begun the long series of additions to the planetary system, which has continued without interruption up to the present time. Not one year has passed without the discovery of at least one asteroid, and in every year, except five, three asteroids and upwards have been detected. In 1852, eight were discovered; in 1857, nine; and in 1861, no less than ten the largest number ever yet detected in a single year.

The planet, Amphitrite, was detected independently by three observers, on three successive days, viz., by Mr. Marth, at the Regent's Park Observatory, on March 1st, 1854; by Mr. Pogson, at Oxford, on March 2nd; and by M. Chacornac, at Marseilles, on March 3rd.

The discovery of the planet Melese was attended by circumstances of singular interest.

M. Goldschmidt was engaged at Paris in searching for the planet Daphne. This planet had been discovered by him in 1856, but was so unfavourably situated at the time of its discovery that only four views were obtained of it, and the true nature of its path remained doubtful. Goldschmidt, making use of a roughly calculated ephemeris of the planet's motion, was scrutinizing the sky for Daphne, when he detected a minute star, which presently turned out to be in motion. He announced his discovery, and the planet, which every one supposed to be Daphne, was carefully tracked by experienced observers. HowIn some instances, so closely have the ever, when its orbit was calculated, it beheavens been scrutinized by observers in came clear that there was some mistake. different places, that the same asteroid has The planet just discovered had doubtless been detected independently by two observ- been very near the place occupied by ers within a few days or hours of each other. Daphne in 1856, but not at the precise For instance, Mr. Hind detected Irene on point indicated by M. Goldschmidt's obthe night of the 19th of May, 1851, and,servations.

There is so little variety in the records of the discovery of asteroids, that it would be extremely wearisome to our readers if we were to give an account of the detection of all or even of many of the asteroids. But some incidents in the progress of discovery have been well worthy of notice.

A careful computation soon

such an observation as this, because there the massive globe of a primary planet into are many stars which only shine out at in- fragments, and hurled these forth with suftervals. Olbers supposed the stranger to ficient energy to account for the anomalous be one of these fitful variables; but he motions of the recently discovered bodies. thought it well to re-examine the star, after He suggested the possibility that other an interval, in order to see whether it had fragments might be discovered; and he any perceptible motion. He found that it pointed out two parts of the heavens in was moving, and continuing his observa- which the search after such fragments would tions he established the fact that the stran- have the best chance of success. ger was a planet, on the very evening on which he had first discovered it.

The views of Olbers were quickly acted upon, and no very long time elapsed beIn exactly one month from the discovery fore the discovery of a third planet in one of this second planet, Gauss had calcu- of the very regions indicated by Olbers, lated its orbit. To the surprise of the as- seemed to confirm his fanciful theory. tronomical world, the stranger was found The new planet, which received the name to be quite as fitting a representative of of Juno, was detected by Harding, of LilienKepler's missing planet as Ceres had been thal, on September 2nd, 1804. It appears shown to be. Its mean distance is nearly to be smaller than either of the others, and the same as that of Ceres; and its dimen- revolves in an orbit of singular eccentricsions appear to be equally, or perhaps ity. more minute. But the orbit of the new planet presents one or two peculiarities. It is far more eccentric than that of Ceres, and it departs so widely from the mean plane of the planetary system, that Sir W. Herschel considered the term planet inapplicable to such a body. Hence arose the invention of the name asteroid, perhaps as ill-chosen a term as has ever been adopted by the scientific world.

Confirmed in his views by this discovery, Olbers prosecuted the search after new fragments of his shattered planet with new energy. For two years and a half, however, he sought in vain. At length, on March 28th, 1807, his perseverance met with its reward, in the discovery of the largest known member of the asteroidal family. He was examining the northern wing of Virgo, when his attention was drawn to a The circumstance that two planets should brilliant star of the sixth magnitude in a be found revolving around the sun at near- neighbourhood with which his long-continly the same mean distance, attracted a ued researches had made him intimately great deal of attention among astronomers. familiar. He had never before seen this In fact, we may look upon the discovery star, and, therefore, felt convinced that it as one of the most remarkable that has was a planet. It must be remembered that ever been effected. For men began at to a telescopist, sixth magnitude stars hold once to see that there exists within the sol- much the same position as first magnitude ar system a variety of structure of which stars to the naked-eye observer. they had hitherto had little conception. shine out in the field of view just as ArctuIt is not saying too much to assert that a rus, Aldeboran, or Sirius shine out among large proportion of the views at present the lesser stars on the celestial vault. held respecting the planetary system would have been scouted as bizarre and fanciful before the discovery of Pallas. For in astronomy, as in the other sciences, the range of the known limits man's conceptions respecting the unknown.

They

Therefore, a telescopist who has spent any time in examining a particular region of the heavens, would be as much struck by the discovery of a new sixth magnitude star, as any person familiar with the constellations would be if a new and brilliant star were to shine out in some well-known star-group.

So strange did the phenomena presented by the two new planets appear, that asA few hours' observation sufficed to place tronomers were led to suppose that possi- the planetary character of the star beyond a bly these bodies might be but the fraginents doubt. Soon after, Olbers sent to Gauss of a large planet, which had once revolved, a series of observations for the determinabrilliant as Mars or Jupiter, between the tion of the new planet's path, and in two orbits of these planets. Men recalled the hours from the receipt of Olbers' communifanciful views of the ancient astronomer, cation, Gauss had completed the calculation who spoke of planets which had disap- an achievement unexampled in the hispeared from the heavens. Olbers, the dis- tory of physical astronomy. The orbit of coverer of Pallas, was the first to give form the new planet was found to resemble that to the new theory. He supposed that of Ceres, Pallas, and Juno, but its distance some internal convulsion might have rent is somewhat smaller. It is the only aste

roid which has ever been visible to the naked eye, Schroeter being the only observer who has so seen it.

Then for a long time the progress of discovery ceased. It would seem that no further search was made until about the year 1830, when M. Hencke, an amateur astronomer of Driessen, in Germany, began a careful survey of the zodiac belt. For fifteen years he continued to examine the heavens without success. During all those long years he was intent on the study of stars which no unaided eye has ever seen. Laboriously he traced down their configuration, returning again and again to stargroup after star-group in hopes of detecting the signs of change. But it was not until the close of the year 1845, more than thirtyeight years after the discovery of Vesta, that Hencke's unflinching perseverance met with its just reward. On the 8th of December, he wrote to M. Encke, of the Observatory of Berlin, announcing the discovery of a star in a certain position which he felt sure had hitherto been untenanted. Encke examined the heavens in this neighbourhood six days later, with the magnificent refractor of the Berlin observatory, and quickly discovered a star which was not marked in the observatory chart. As in former instances the planetary nature of the stranger, and the fact that it belongs to the same region of space already assigned to the other asteroids, were quickly established. Encke left the choice of a name with Hencke, who selected the name Astræa.

With the discovery of another planet by M. Hencke, in July, 1847, may be said to have begun the long series of additions to the planetary system, which has continued without interruption up to the present time. Not one year has passed without the discovery of at least one asteroid, and in every year, except five, three asteroids and upwards have been detected. In 1852, eight were discovered; in 1857, nine; and in 1861, no less than ten -the largest number ever yet detected in a single year.

There is so little variety in the records of the discovery of asteroids, that it would be extremely wearisome to our readers if we were to give an account of the detection of all or even of many of the asteroids. But some incidents in the progress of discovery have been well worthy of notice.

In some instances, so closely have the heavens been scrutinized by observers in different places, that the same asteroid has been detected independently by two observers within a few days or hours of each other. For instance, Mr. Hind detected Irene on the night of the 19th of May, 1851, and,

four days later, M. Gasparis, of Naples,
detected the same asteroid.
Within a year,
M. Gasparis had his revenge, however.
On the 18th of January, 1852, Mr. Hind
marked down in the ecliptical chart which
he was compiling, with the aid of Mr. Bish-
op's refractor, at the Regent's Park Obser-
vatory, a star of the eleventh magnitude.
Cloudy weather prevented him from re-ex-
amining this object for exactly two months.
On the evening of March 18th, he turned
his telescope to the spot which had been oc-
cupied by the small star; but the star had
vanished. Immediately he instituted a
searching scrutiny for the missing object,
and would probably soon have detected it.
But, while the search was in progress, news
came of the discovery of an asteroid, in
this particular region of the heavens, by M.
Gasparis. Professor Gauss was able to
show that this object must on January 18th
have occupied the exact place in which
Hind had seen a telescopic star. In this
case, although Hind had not been able to
detect the missing object, he would have
been credited with the discovery of a new
planet had he missed the star one day earlier.
As it was, De Gasparis, having detected
the planet on the 17th of March (one day
before Hind suspected its planetary nature),
is entitled to the credit of the discovery.

The planet, Amphitrite, was detected independently by three observers, on three successive days, viz., by Mr. Marth, at the Regent's Park Observatory, on March 1st, 1854; by Mr. Pogson, at Oxford, on March 2nd; and by M. Chacornac, at Marseilles, on March 3rd.

The discovery of the planet Melese was attended by circumstances of singular interest.

M. Goldschmidt was engaged at Paris in searching for the planet Daphne. This planet had been discovered by him in 1856, but was so unfavourably situated at the time of its discovery that only four views were obtained of it, and the true nature of its path remained doubtful. Goldschmidt, making use of a roughly calculated ephemeris of the planet's motion, was scrutinizing the sky for Daphne, when he detected a minute star, which presently turned out to be in motion. He announced his discovery, and the planet, which every one supposed to be Daphne, was carefully tracked by experienced observers. However, when its orbit was calculated, it became clear that there was some mistake. The planet just discovered had doubtless been very near the place occupied by Daphne in 1856, but not at the precise point indicated by M. Goldschmidt's observations. A careful computation soon

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