yune rg, 1879] 



NATURE 



181 



the altitude of the star at emersion will be 7|°, and at 

 Edinburgh sj^ , , ,. . 



Suppose, for the sake of an example of the application 

 of the above formulae, it is desired to know the Greenwich 

 mean times of immersion and emersion of Antares as 

 viewed from Brighton, which place we will assume to be 

 in latitude 50° 50' and longitude om. 32s. west of Green- 

 wich. We have then L = + o°-83, and M = - o'SBm ; 

 it will be sufficient to include the second decimal only in 

 the factors for l and M in the formulae :— 



For the immersion — 



The sum + 0'56m., added to 

 9h. 36'86m., gives 9h.'37"4m. 

 for G.M.T. 



(+ 0-83) K (+ 0-84) = + 070 

 (-0-53) X (+0-26)= -0-14 



For the emersion — 



(4- 0-83) X (-2-51) =-2-o8 

 (- 0-S3) X (+0-46) =-0-24 



The sum — 2"32ni., added to 

 loh. io'74m., gives loh.S"4m. 

 for G.M.T. 



Similarly the angles will be found to be 152° at 

 immersion and 202° at emersion. 



The companion of Antares preceding the principal 

 star nearly on the parallel will emerge several seconds 

 earlier. 



The Great Comet of 1874. — Just five years since, as 

 we write, the comet discovered by M. Coggia at the Ob- 

 servatory of Marseilles on April 17, 1874, was baginning 

 to attract general attention as a naked-eye object in the 

 evening sky. The orbit, the determination of which pre- 

 sented some difficulty at first, from the slow motion of the 

 comet, had been ascertained with sufficient precision to 

 enable astronomers to predict its conspicuous appearance 

 in the first half of July, and the track it would follow when, 

 descending below the horizon in Europe, it became a 

 favourably-situated object for the observatories of the 

 other hemisphere. It was observed in Europe until July 

 16, and about a week later was seen in Australia ; obser- 

 vations were continued till October, the last being made 

 at the Argentine Observatory, Cordoba, on the i8th of 

 that month, when it had receded to a distance of i -94 from 

 the sun and 1 79 from the earth, and was situate about 

 12"' from the south pole of the heavens. 



The European observations during three months were 

 found to indicate a sensible, though not very material 

 deviation of the orbit from a parabola, and ellipses were 

 calculated at the time by Tietjen, Schulhof, and Geel- 

 niuyden. In a late number of the AstronomiscJie Nach- 

 richten are elliptical elements founded by M. Seyboth, of 

 Riga, upon the meridian observations made at Moscow, 

 which appear to possess a very high degree of precision, 

 though they extend over an interval of twenty-six days 

 only. The periods of revolution assigned by these com- 

 puters arc : — 



Tietjen ... 

 .Schulhof ... 

 Geelmuyden 

 Seyboth ... 



8,965 years. 

 12,184 .1 

 10,445 .. 



S.711 .. 



The differences between these periods show that beyond 

 estabhshing the fact that the comet was moving in an 

 orbit with a period of revolution extending to several 

 thousand years, no reliable approximation to its true 

 length has yet been obtained, but the additional three 

 months' observations in the southern hemisphere have 

 not hitherto been brought to bear upon the determination 

 of the elements. The last Cordoba observations give the 

 following final position : — 



1874, October 18, at I4h. 46™. 58s. G.M.T. 



Apparent Right Ascension 

 ,, Declination 



99 46 27'0 



-77 42 36*6 



If we compare the elements of Geelmuyden and Seyboth 

 with this observation, taking aberration into account, we 

 find the following differences : — 



Error in R.A. 



Error in Dec!. 



Geelmuyden -t- 31 +65 



Seyboth +59 +99 



so that while, as tested by this single observation, the 

 longer period of revolution appears to have the advan- 

 tage, it is sufficiently evident that ellipses with divergent 

 periods may eventually be found to represent the obser- 

 vations with almost equal precision, or in other words the 

 length of the revolution will remain open to considerable 

 uncertainty. If the deviation of the form of the orbit 

 from the parabola, which satisfies the motions of the 

 majority of comets be due to planetary attraction, we 

 might look to Venus as the agent, since at the descending 

 node the comet in 1874 approached the orbit of that 

 planet within 300,000 miles (0-00325 of the earth's mean 

 distance) ; the opposite node falls at a radius-vector of 

 1 1 '65. The aphelion distance, according to Geelmuyden's 

 calculation would be 95 5 'o, or the comet would have 

 travelled to these parts of space from a distance exceeding 

 by more than thirty times the mean distance of Neptune. 



GEOGRAPHICAL NOTES 



The Abbd Debaize, who by previous accounts was at 

 Igonda on March 20, seven days' journey from Ujiji, 

 has written under date of April 2 from the latter place 

 to the director of the Paris Observatory and others, 

 giving a brief sketch of his immediate plans. He pro- 

 poses to take all his porters and merchandise by water to 

 the Uzighd country at the north end of Lake Tanganyika, 

 and to form a depot there, which he will leave in charge 

 of some of his best men ; he will then estabUsh a second 

 depot at the mouth of the Aruwimi, the great northern 

 tributary of the Congo. Afterwards, starting in light 

 marching order, he hopes to be able to explore the 

 western slopes of the Blue Mountains, the countries 

 situated between the southern end of Albert Nyanza and 

 Like Tanganyika, and especially Unyambongu, Mpororo, 

 and Ruanda. He will then return to his depot in Uzighe, 

 whence he will send home an account of his discoveries, 

 as well as a statement of his future plans. 



An interesting and extremely well written pamphlet has 

 just appeared in the "Sammlung gemeinverstandlicher 

 wissenschaftlicher Vortriige," edited by Prof. Virchow 

 and Herr von Holtzendorff'. Its title is "Die Tiefsee 

 undihreBoden und Temperatur Verhaitnisse," its author 

 Dr. Georg von Boguslawski, the well-known editor of the 

 Aiinakn der Hydiographie at the Imperial Admiralty of 

 Berlin. The writer first gives a clear and concise account 

 of all expeditions sent out by various countries for the 

 investigation of the depths of the sea, particularly those 

 of the Gazelle, the Challenger, and the Ttiscarora. He 

 then enters at greater length upon a discussion of the 

 results obtained hitherto, treating first of the depths them- 

 selves, then of the outlines and physical condition of the 

 sea-bottom, and finally of the distribution of temperatures 

 and the inter-oceanic currents, with .their causes and 

 effects. Our space does not permit us to enter into details 

 at greater length, suffice it to say that the little work is a 

 welcome and valuable addition to scientific literature. 



The Geographical Department of the Japanese Go- 

 vernment, which is displaying considerable activity in 

 many directions, has commenced the publication in 

 sheets of a large plan of the city of Yedo, showing the 

 various divisions, streets, bridges, &c., and giving the 

 names in Japanese and Roman characters. 



Under the title of " Voyage d'Exploration dans ITn- 

 tdrieur des Guyanes," the Tourdu Monde has commenced 

 the publication of Dr. Jules Crevaux' account of his 

 Journey in 1876-7 through French Guiana and across the 

 Tumac Humac range to the .Amazons. The illustrations 

 are very interesting and well executed, and there is also a 

 sketch map of the region. 



