June 12, 1879] 



NATURE 



157 



the observations, proportionally small variations in the 

 elements producing greatly magnified effects upon the 

 geocentric place and geocentric motion, in consequence 

 of the close proximity of the comet. 



Oppolzer describes his method of calculation in No. 1,938 

 of the Astronomischc Nachrichte?i, to which we must 

 refer the reader, as an outline of it would unnecessarily 

 extend this note. He makes three assumptions as to the 

 distance of the comet from the earth and deduces three 

 orbits for comparison with the orbit of Biela's comet, as 

 follow : — 



(A) (B) (C) 0^^|,°f 



Distance assumed ... 0"04 o"o8 0'I2 — 



Mean anomaly - 4 54"4 - 5 6'8 - 5 4-8 — 



Long, of perihelion ... 128 48 141 9 151 50 109 45 



,, ascending node 247 38 244 34 242 12 24S 50 



Inclination 9 14 10 28 11 46 12 22 



Angle of excentricity.. 51 36 54 17 56 49 48 48 



It must be added that Oppolzer pre-supposes the comet 

 moving in an orbit with same semi-axis major as that of 

 Biela, the corresponding mean daily motion being"53o"'i ; 

 hence with the above mean anomalies on December 3'o, 

 the dates of perihelion passage on the three hypotheses 

 would be respectively January 5 '3, January 67, and 

 January 6'5. 



The similarity of these systems of elements is striking ; 

 only in the longitude of perihelion are there compara- 

 tively large differences, which Oppolzer observes, may 

 not appear so noteworthy when it is remembered that 

 Michez's elements do not include the effect of perturba- 

 tions from 1866 to 1872, nor those which might just have 

 resulted from the presumed exceedingly close approach 

 of the comet to the earth on the night of the meteoric 

 shower. The great difference of nearly three months in 

 the perihelion passage, however, he regarded as against 

 the identity of the object with Biela's comet, though from 

 the anomalies which the disintegration of the comet might 

 have occasioned, this circumstance might not really pos- 

 sess all its apparent signification. His general conclu- 

 sions may be stated thus : — It may be asserted with 

 confidence that assuming the distance of Pogson's comet 

 from the earth December 3'o to have been within the 

 limits o'o4 and o'i2 of the earth's mean distance from the 

 sun, we are led to elements which show a remarkable 

 resemblance to those of Biela' s comet, as well as with the 

 coiurse of the great shower of meteors on November 27, 

 1872. When the distance is much increased we find 

 materially different elements, and the greater distance 

 cannot be regarded as improbable ; in this, Oppolzer 

 remarks, lies in his opinion the weakest point of the 

 argument, and only by observations at a future time can 

 a certain conclusion be attained. Nevertheless he con- 

 siders the striking coincidences following on arbitrary 

 assumptions, taken together, militate strongly in favour of 

 the approximate correctness of his assigned distance. Thus 

 there seems to be under the above suppositions as to the 

 comet's distance, a most remarkable connection with the 

 meteor-shower of November 27. If, as a rough approxi- 

 mation, it is assumed that the comet at 8 P.M. on that day 

 touched the earth, and further, that the differential daily 

 variation of the distance within the 55 days was equable, 

 an hypothesis, which in the case of a contact, will not 

 differ much from the truth, there will be deduced from 

 the three values, for the distance of the comet on 

 December 3, respectively o-o6i, 0071, and o'oSo; com- 

 paring these values with those assumed, it is seen at once 

 that an agreement is established with the final value, 

 when the distance = 007 nearly. This result Oppolzer 

 urges as highly deserving of note, and in his opinion 

 almost demonstrates the connection of the swarm of 

 meteors with the comet. On the supposition that the 

 true values of the elements must be sought between the 

 systems (a) and (ii), considering further that the earth- on 



November 73 was in 65°'9, heliocentric longitude, and 

 that the comet if it gave occasion to the meteor-shower 

 must have been situate near its descending node, so the 

 longitude of the node by this criterion would be 245°'9, ^ 

 value which also falls between the limits (a) and (b). 



Further, if the distance of the comet from the earth is 

 calculated from the above elements for the time of the 

 meteor-shower, the following series is formed : — 



ABC 



0*024 o'oog 0*053 



and it is seen that the assumption of 0*07 for the distance 

 on December 3, leads to a very close approximation of 

 the comet to the earth at the time of the shower. Calcu- 

 lating now the comet's radius-vector for November 27*3, 

 the three systems give logarithmically — 



ABC 



o'o042 9'99So 9"99o8 



while the log. distance of the earth is 9*9940. Conse- 

 quently with elements A and B the comet is a little out- 

 side the earth's orbit, and with elements c it would occupy 

 a position within it. At the first glance it will appear 

 probable that necessarily the last relation must have 

 place, or the comet would certainly have been detected 

 ere it reached its least distance from our globe. On the 

 one side, from the uncertainty of the data for calcula- 

 tion, the results may be considerably in error, on the 

 other there may be some probability that the comet was 

 visible in the southern hemisphere, and v,-e might have 

 received intimation that a comet of great brightness and 

 with rapid motion was there recognised. Calculating 

 from the three systems of elements the geocentric place, 

 there result — 



ABC 



A 67° no" iSo* 



3 ■ +11 - 75 - 25 



so that, in fact, with the system B, which appears to ap- 

 proach nearest the truth, the circumstances of visibility 

 for the southern hemisphere would be favourable. 



Weighing all these circumstances, Oppolzer thought it 

 must be granted that Pogson's comet stands with high 

 probability in intimate relation with the meteor-shower of 

 November 27, and that it is possible the observed object 

 was one of the heads of Biela. That the second head 

 was not found, is not decisive against this, since the same, 

 on account of close proximity to the earth, might have 

 been situate in an entirely different quarter of the heavens, 

 and besides, from its greater relative distance, might have 

 been considerably fainter, so as easily to escape detec- 

 tion. Thus, at the time of writing his paper on the sub- 

 ject, Oppolzer was of opinion that the connection of 

 Biela's comet with Pogson's object and the meteor- 

 shower was by no means to be regarded as improbable. 



GEOGRAPHICAL NOTES 



The Golos publishes a telegram, dated the 13th of May, 

 from the celebrated Central Asian traveller, M. Prjevalsky, 

 formerly a colonel in the Russian army. At that time he 

 was on the river Buluguna. He had marched 600 versts 

 from Saisan along the river Urumtsu, and would imme- 

 diately set out for Chemi through the southern Altai 

 mountains. All the members of his expedition were in 

 good health. 



The Alexandria correspondent of the Daily News sends 

 some details of Major Serpa Pinto' s recent journey across 

 Africa from Benguela to Durban. He tells us little that 

 has not been already made known, and we shall look with 

 eagerness for Pinto's promised.work. Science has evidently 

 had considerable attention! rom Major Pinto during his 

 journey. He has brought home a collection of 1,800 

 plants and " a superb collection of birds and insects." 

 Astronomical and meteorological observations have been 

 taken along the route, and several volumes of notes made, 

 with maps. The Coando, which flows into the Zambesi, 



