AND OF THE PHYSICAL SCIENCES. 



11 



■JTeteoric Stones. — It has only recently been discovered that copper forms an 

 ingredient of meteoric stones. Hofrath Stromeyer asserts that it exists in all me- 

 teoric masses. He has examined specimens from Agram, Lenard, Elbugen, Bilburg, 

 Siberia, Gotha, Louisiana, Buenos Ayres, Brazil, and the Cape of Good Hope, and 

 detected in them all an appreciable quantity of copper, varying from one-tenth to one- 

 fifth per cent. He has come to the conclusion that the presence of copper must be 

 considered as a constant character in these substances, as are the nickel and cobalt, 

 which are found in greater proportions.* 



H. Stromeyer examined a meteoric mass, found at Magdeburg in 1831, the spe- 

 cific gravity of which was 7.39, and which contained 4.32 per cent, of copper. An- 

 other mass was found near the Iron "Works of Rothchutte, in the Hartz, conta,ining 

 7.69 per cent, of copper. 



The celebrated chemist Berzelius, who analyzed a mass of meteoric stone from Ma- 

 cedonia, did not detect copper as forming part of its substance. Its ingredients were, 

 silica 39.56, protoxide of iron 13.83, and peroxide of iron 5.00, making a total of 

 iron 18.83. Alumina 2.70, oxide of chromium 0.50, Hme 1.S6, magnesia 26.30, 

 oxide of nickel 0.10, oxide of manganese 2.40, potash 2.08, soda 1.20; making a 

 total of 95.53. Besides the above substances, Stromeyer has detected copper, cobalt, 

 arsenic, phosphorus, sulphur, sihcon, and carbon. 



Lightning. — The Medical Gazette of St Petersburgh states, that the life of a 

 soldier, struck by lightning, has been saved by copious bleeding. 



GENERAL SCIENCE. 



NO. L— ON THE COMET OF HALLEY, SOMETIMES CALLED 

 THE COMET OF 1759. 



BISTORT OF THE COMET TO A.n. 1456. 



Hast thou ne'er seen the comet's flaming flight? 

 Th' illustrious stranger passing, terror sheds 

 On gazing nations, from his fiery train 

 Of length enormous; takes his ample round 

 Through depths of ether; coasts unnumber'd worlds 

 Of more than solar glory; doubles wide 

 Heaven's mighty cape, and then revisits earth. 

 From the long travel of a thousand years. 



YOUNG. 



[The foUo'vlng is the first of a series of papers, drawn up chiefly from the works of 

 M. Arago, and of ISI. de Pontecoulant, upon this interesting heavenly body which 

 has just vis. ted us.] 



Tire first appearances of this comet are unrecorded and unknown. Its origin, like 

 that of the most powerfu). empires of the earth, or of the greater number of extraor- 

 dinary men, who have astonished and enlightened the world, is enveloped in profound 

 darkness. Historians, influenced by the universal terror which these bodies for- 

 merly inspired, have given an exaggerated tone to their descriptions; and that pro- 

 pensity to assign unusual events to supernatural causes, when the explanation of them 

 surpasses the human understanding, has long induced mankind to consider these stars, 

 and their long train of attendant light, as evident signs of celestial wTath. They have 

 been viewed as the messengers of destruction — the forerunners of the three greatest 

 plagues which can desolate the earth — war, pestilence, and famine. Some comets 

 were even thought to have been appointed on the special mission of presiding at the 

 birth or death of those distinguished mortals, whom we may, without impropriety, 

 style meteors of a moral order. Such was the extraordinary comet that appeared 

 during seven days at the death of Julius Cresar ; and also that equally remarkable 

 one, seen at Constantinople in the year signalized by the birth of Mahomet. We may 

 therefore infer, that historians of those times, being under the influence of popvUar 

 superstitions, viewed with a partial eye the comets they describe; or, at least, they 

 seem to have greatly exaggerated the circumstances attending their appearances. In- 

 deed, ever since these bodies have been examined without prejudice, and for scienti- 

 fic purposes alone, we no longer see them extending from east to west, covering one 

 entire portion of the celestial sphere. No longer does their fearful hue appear to re- 

 flect, by anticipation, the blood-stained field of battle, or the flames of approaching 

 conflagrations. Since, then, we have no other guide than these faithless accounts of 

 cotemporary writers, it becomes very difficult, at the present time, to recognize the 

 more sober visitants of the last two centuries among these denizens of a fairy sphere. 

 An account drawn up with fideUty, wherein the physical appearances of a comet are 

 exactly described, may be sufficient to establish a general probability, that two of these 

 bodies, observed at different periods, are identical j yet, as we shall hereafter show, it 

 is wholly inadequate to prove their identity. 



The PERIOD of a comet is that portion of time which elapses between its two con- 

 secutive returns. That of Halley, the subject of these papers, reappears at intervals 

 of time, the mean, or average of which, is about seventy-five years and a half. By 

 counting backwards, it has been thought to correspond sufficiently near with that 

 which appeared at the birth of Mithridates (a.c. 130), The comet of Mithridates — 

 the most extraordinary of any that have ever been seen or described — exhibited itself 

 for eighty days: its splendour surpassed that of the sun, its size occupied a fourth 

 part of the heavens, and it took four hours in rising, and as many in setting! An 

 origin so illustrious would not h?.ve been unworthy of a comet, occupying a place so 

 important m the history of astronomy. But, after we have made all the necessary de- 

 ductions for the tone of exaggeration evidently impressed on this account, the identity 

 of the comet of Mithridates with that of Halley is still V3ry doubtful, as it has been 

 assumed, in the calculation, that the comet of 1759 returned periodically at equal 

 intervals of time. 



In the year a.d. 323, a comet was observed In the constellation Virgo (the virgin), 

 which Jippaars to have had some resemblance to that of Halley. All the historians of 



• Ann, Der Physik., xxvii. p. 689. 



the Constantinopolitan empire allude to a comet seen at an interval of 76 years 

 after the former, in the year a.d. 399. The coincidence of the period would lead us 

 to consider this body to be identical with the comet of 1759, and to infer that one of 

 the periods of its return to the neighbourhood of the sun is here pointed out. This 

 comet was said to have exhibited some extraordinary characters. Lubienietski {The- 

 atrum Cometarum) describes it as being of prodigious size, of frightful aspect, and 

 seeming to dart its hair even to the earth. '* Cometa fuit prodigiosaj magnitudinis, 

 horribihs aspectu, comara ad terram usque -demittere visus." Again, we hear of a 

 comet in a.d. 550; — and that nothing marvellous might be wanting to its history, the 

 return coincided with the taking of Rome by the Goths, under Totila; and it 

 was, of course, considered by a credulous people as one of the causes of that event. 

 After an interval of 380 years (a.d. 930), historians speak of a star, which we may 

 again suppose to be the same comet, after having performed five revolutions during 

 that time. It reappeared at its following return (a.d. 1005) ; and after passing over 

 three periods, we find, from the list of 415 comets which Lubicnietski has described, 

 that in the year 1230 a comet was observed, which may have been the same with 

 that of Halley. But it is no longer possible to follow the comet through the obscu- 

 rity and ignorance of the middle ages. In those times of bai'barity, the physical ap- 

 pearances of the heavenly bodies were either not observed, or distorted by the de- 

 lusive medium through which they were viewed. We have already explained, that 

 our only means of establishing the identity of Halley's comet with those recorded in 

 ancient writers, is the constant periodical return of the comet of 1759, at equal pe- 

 riods of time. But the periods of this star are continually, and must essentially vary, 

 as we shall hereafter show, by the interval of about one year or eighteen months. 

 We cannot, therefore, place implicit reliance upon the preceding calculations, deduced 

 from a principle which is not in itself strictly exact. In addition to this, there are 

 some years when a great number of comets are lisible. At present, a year does not 

 elapse, without some comet being remarked at the different observatories of Europe. 

 It is therefore absolutely impossible to decide, whether the comet of 1759 is really 

 identical with those, whose appearances are stated to have been so extraordinary in 550 

 and 399; or whether it did not pass, during these or neighbouring years, without 

 attracting the attention of common observers, who would have been entirely engrossed 

 with other more remarkable phenomena. It is, therefore, only with the utmost re- 

 serve that we have ventured to suggest these analogies between the present comet 

 and similar bodies which have appeared before the thirteenth century. We have re- 

 lated these circumstances, more as matters of curious research than of positive truth, 

 upon the faith of those learned men who have sought the annals of antiquity for traces 

 of Halley's comet. Like some historians, who love to surround the cradle of their 

 favourite hero with circles of light and lambent flames, we expose the legends of an- 

 tiquity. It is. in fact, only about two centuries ago that comets were first observed 

 with care ; and, previous to that time, the tales related of them are exceedingly doubt- 

 ful. 



Let us return to the uncertain history of this comet. — In the year 1305, there ap- 

 peared one of these bodies, which would correspond in character with the comet of 

 Halley. The chroniclers of the times gave a tremendous description of it. *' Come- 

 ta horrendce magnitudinis visus est circa ferias Paschatis, quom secuta est pestilentia 

 maxima." (A comet of dreadful magnitude was seen about the Easter holidays, which 

 was followed by a pestilence of the worst description.) The concluding observation 

 throws a doubt upon the exactness of the whole statement; and, as Lalande has ob- 

 served, it is very possible that fear of the pestilence may have increased the impres- 

 sions left by tlie comet. However, it is but right to state, that from the position 

 which the comet of 1759 occupied in its orbit, it must have passed very near to the 

 earth during the year 1305 : this would have given it an appearance of unusual mag- 

 nitude. 



In the catalogues of Alstedius and of Lubienietski, there are two comets men- 

 tioned, one in 1379, and another in 1380, separated from the former by an interval 

 of about 75 years; but as no details are given of the time, place, or form of their 

 appearances, nothing satisfactory can be ascertained. 



The same comet reappeared in 1456, and was accompanied by several remarkable 

 circumstances, *' Cometa inauditaj magnitudinis toto mense Junii apparuit cum pro- 

 longa Cauda, ita ut duo fere signa coeli coraprehenderit." (A comet of unusual magni- 

 tude appeared during the entire month of June, with a tail of so great length that it 

 covered nearly two entire signs of the heavens.) It is possible that the length of this 

 tail may be a Uttle exaggerated, especially as the visible part of the heavens is ISO"^, 

 and a sign is 30'=*. Yot we must allow that there was something grand in its appear- 

 ance ; because it had the effect of spreading, at this epoch, as great a terror throughout 

 all Christendom, as the rapid progress of Mahomet 11., who had just made himself 

 master of Constantinople. The Pope, Calixtus II., with a-n economy of labour re- 

 markable for the age, exorcised the comet and the Turks in the same Bull, and ordered 

 public prayers, with a formula, to be made, which might include them both. Not- 

 withstanding these efforls of his Holiness, Mahomet and the comet contmued their 

 several courses; the former succeeded in converting the Cathedral of Sancta Sophia 

 into his principle mosque; and the latter vanished peaceably into the infinity of 

 space. 



The great length of tail ascribed to the comet of 1456, and the consternation which 

 it diffused throughout benighted Europe, have led scientific men to consider it in n- 

 otht-r point of view. They have ascertained the position which a comet must occupy, in 

 order that it may appear of the greatest possible briUiancy; and the result is, that this 

 comet, from its near approach to the sun, and from its situation relative to the earth, 

 must have united all the conditions necessary to that appearance of splendour assigned 

 to it by the chroniclers of the times. 



Although no precise observations upon this phenomenon have been handed down to 

 us, yet the time when the comet appeared, and the course which it held, are described 

 with sufficient accuracy ; so that Dr Halley did not hesitate to assert its identity with 

 the comets of 1531, of 1607, and of 1682. This appearance of 1456 ought, there- 

 fore, to be clearly distinguished from all those preceding it, and to be considered as 

 a remarkable epoch in the history of science. 



