178 



NATURE 



\yune 23, 188] 



Putting d h. for the correction of the difference of R.A. betv\een 



the Sun and Venus, i/D for the correction of the difference of 



declination, and dv for that of the assumed value of the parallax 



(8""848) the solution of the equations of condition corresponding 



to the distances gives — 



i/A= + i"'iSi ... fl'D=+2"'225 ... </7r= +o"-o397±o"-04iS 



Similarly from the equations corresponding to angles of position 



there result — 



flrA= + i""i09 ... fl'D=+o"-637 ... (/ir= +o"'0252±o'''0S95. 



Combining these values, the final results become — 



r/A= +05-076 ... fl'D=+2"-o83 ... <^5r= +o"-035±o"-o34, 



and the corrected value of the solar parallax is thus 8"'SS3. It 



will be seen that the magnitudes of the probable errors are very 



large in proportion to the corrections obtained. 



Biela's Comet in 1805. — Those who have acquainted them- 

 selves with the history of this remarkable comet will remember 

 that at its appearance towards the end of 1805 it was last 

 observed in Europe by Thulis at Marseilles on the evening of 

 December g, at w hich time it was at its least distance from the 

 earth, and was moving rapidly southwards. The comet was 

 then visible to the naked eye, and it was known that it woukl 

 probably continue so for some days, and might attract attention 

 in the other hemisphere. But there was no southern observatory 

 in existence at that time. Prof. Hubbard, in his masterly 

 investigation on the motion of Biela's comet, remarked how 

 greatly observations taken in the southern hemisphere at this 

 appearance might have contributed to the progress of the theory 

 of the comet. Gauss was then applying his methods for the 

 determination of elliptic orbits, or rather of orbits without the 

 assumption of a particular conic section, and it could hardly 

 have happened that viith good southern observations the nature 

 of this comet's orbit w ould not have been detected from the 

 observations of 1805, and the comet might thus have been 

 re-observed in 1812, if not in 1S19. 



Up to a quite recent date it was not known that the comet had 

 been observed in the other hemisphere, but Prof. Winnecke has 

 discovered (where he does not say) some observations m-ide at 

 the Mauritius by MM. Malavois and Dupeloux on December 14 

 and 1 5. They were brought to light while he was inquiring into 

 the periodicity of the comet detected at Strassburg by Dr. Hart- 

 wig on September 29, 1880, and he gives an account of them in 

 the last number of the Vierleljahrsschrift der Astronoimschcn 

 Gesellschaft. They are entitled "Observations sur la Comete 

 qui a paru a File de France dans le cours de frimaire au 14"= par 

 M. Malavois et M. Dupeloux." M. Malavois states that he was 

 apprised of the appearance of the comet on the morning of 

 December 14. ^Four days previously {and therefore the day after 

 it was last seen in Europe) it had been detected by MM. Laprie 

 and Dabadie, the one a censor, the other a professor of the 

 colonial Lycee : they had remarked that it had passed in a very 

 short interval " over the space between the constellations Grus 

 and Pavo, moving almost from north to south." On the evening 

 of December 14 Malavois " avec un excellent sextant a lunettes 

 d'un pied de rayon," measured the distance of the comet from 

 Achernar and Canopus, and the distance between the ;tars, and 

 Prof. Winnecke haa been at the trouble to reduce these observa- 

 tions accurately, and to compare them with Hubbard's elements 

 with the aid of an ephemeris calculated therefrom by Herr 

 Kaufmann. Referring to the above-mentioned periodical for 

 particulars, we may say that Hubbard's orbit is found to place 

 the comet too much to the west by 13' in right ascension, and in 

 declination one minute to the north. But while giving these 

 differences between calculation and observation. Prof. Winnecke 

 only aims at proving that Biela's comet was recognised in the 

 southern hemisphere, and well observed, considering the means 

 available. 



The de.-cription of the comet's appearance given by Malavois 

 is worthy of particular remark : — " Cette comete est photo- 

 spherique, cad. entouree d'une sphere lumineuse dont le 

 diametre m'a .^emble etre en totalite d'environ 45 minutes : 

 mais la partie la plus lumineuse, ou I'aureole vue au commence- 



ment du crepuscule du soirn'etoit guere, que de 20 .a 25 minutes ; 

 on la distinguoit alors tres bien, tandis qu'a peine on pouvoit 

 apercevoir les etoiles de 7""^ grandeur. La comete vue avec 

 une lunette qui grossit seize fois le diametre des objets m'a paru 

 divisee en deux par une petite band obscure ; j'ai jugi son 

 diametre apparent d'environ une minute, mais les bords m'ont 

 semble confu^ement termines et te foudre avec la lumiere 

 ucbuleuse ; une etoile de 4= a 5^ grandeur que je distinguais tres 

 bien dans I'aureole a 4 ou 5 minutes de la comete, s'est trouvee 

 dans une position et une distance differente par rapport a cet 

 astre dont le mouvement propre etoit en effet considerable, 

 comme on la voir." Malavois' observations were limited to the 

 evening of December 14, absence preventing his observing it on 

 the following night, and clouds interfering ou December 16 and 

 17 ; and he adds : " les jours suivans j'ai cessede I'apercevoir.'' 

 Prof. Winnecke draws attention to the remarkable appearance 

 of the comet under a power of 16, in the evidently small tele- 

 scope, and asks ; " Can we recognise in the ' petite bande obscure,' 

 which divided the head into two parts, the commencement of 

 the action which kd to the highly important result, that in 1S46 

 and 1852, instead of a single comet, two were observed, and 

 laler the comet has been no longer visible as such." In connec- 

 tion with the Mauritius observation it must be remembered that 

 the aspect of the comet was particularly noted on December 8, 

 when it was nearer to the earth than on December 14, by Olbers, 

 Bessel, and Gauss, who agree in their description : on the same 

 evening it was examined and measured by Schroeter with power- 

 ful reflecting telescopes at Lilienthal. Neither observer has any 

 reference to the appearance of a division in the head of the 

 comet on that date. Olbers says "it had a small but very dis- 

 tinctly defined nucleus, surrounded by an extensive nebulosity, 

 without any appearance of a tail." The comet w as visible to 

 the naked eye with the brightness of a star of the third or fourth 

 magnitude, and could be well seen after the moon had risen. 

 Schroeter noted that without the telescope it appeared nearly as 

 large as the moon : in his 13- and 15-feet reflectors it was appa- 

 rently much diminished, his measures giving a diameter of only 

 54 minutes ; the diameter of the brightest part of the nucleus he 

 found to be 4"'05, and that of the w hole nucleus 6"'42 ; if a 

 division had existed at the date of these measures it is hardly 

 probable that it would have been overlooked by Schroeter. At 

 the reai'pearance of the comet in 1S26, and again in 1832, 

 nothing of the kind va as remarked. Hubbard, we know, cou- 

 sic'ered that the division of the comet, from whatever cause it 

 might be produced, took place at the end of the year 1844. 



GEOGRAPHICAL NOTES 



The hydrographical expedition for the exploration of the 

 mouth of the Obi River has started from St. Petersburg. It 

 consists of four officers of the navy, one astronomer, M. Fuss, 

 and two students of the St. Petersburg University, one of whom 

 is a surgeon and the other a zoologist. Two small steamboats 

 were sent to I'erni, on the Kama River,'and they will be trans- 

 ported to the Obi. 



Herr Siegfried Langer of Vienna is about to undertake 

 an exploring tour in Arabia ur.der the auspices of the Vienna 

 Geographical Society. His researches will be mainly of a 

 linguistic nature, but icientific re;earch is not excluded from his 

 programme ; he has prepared himself for the tour during the last 

 few years at the Vienna University. 



The geographical department of the British Museum during 

 the past year was deprived of the services of its able curator, 

 Mr. R. H. Major, through ill-health, and on his retirement the 

 opportunity w.as taken to reduce it to a sub-department. If we 

 may judge by the newly piublished report of the British Museum, 

 this change has not tended to increase activity in geographical 

 matters, and among the most interesting acquisitions of the past 

 year all that can be mentioned seem to be some old plans of 

 towns and the like. 



In the last volume of Consular Reports S. de Zuccato at 

 Venice furnishes an interesting map showing the lines proposed 

 and in course of construction for the completion of the network 

 of railways in Venetia. M. Consul Eernal also contributes a 

 plan of the Havre docks. 



It is announced that the Portuguese travellers, Capello and 

 Joens, are about to publish an account of their expedition under 

 the title of " De Benguella as terras d'lacca." The work will be 



