A. MATHEMATICS AND ASTKONOMY. 49 



of the heavens essentially deficient in cometary emanations, 

 although possibly the deficiency of cometary aphelia in this 

 region may depend, to some extent upon the fact that the at- 

 mospheric conditions in July and December are unfavorable 

 to the discovery of comets in that part of the ecliptic. The 

 first of these suggestions, however, will be seen to have some 

 probability, if we consider that Sir John Herschel, who has 

 worked on the distribution of the nebula?, has shown that the 

 various regions of the heavens are very unequally favored 

 as regards the actual quantity of nebulous matter; and a 

 similar inequality in the distribution of those nebulous cen- 

 tres whence comets emanate might from analogy be reason- 

 ably expected. Bullet. Ilebd. Assoc. tScien., 1875, 234. 



BRUHNS OX POGSON's AND BIELA's COMETS. 



The return of Biela's comet in 1872 was, as will be re- 

 membered, looked forward to with great interest, and some 

 disappointment even was felt that it continued invisible to 

 the most powerful telescopes employed in the search for it. 

 Under these circumstances, a faint interest was awakened 

 by the fact that on the 27th of November one of the most 

 beautiful showers of shooting-stars was observed, and that, 

 too, in such a position that it seemed probable that these 

 meteors were moving precisely in the orbit of Biela's comet. 

 There was, therefore, a strong presumption that an intimate 

 connection existed between the two phenomena. Klinker- 

 fues, of Gottingen, suspecting that, in fact, the two might be 

 identical, telegraphed to Pogson at Madras, on the 30th of 

 November, the following dispatch : " Biela touched the earth 

 November 27. Search near Theta Centauri" Following the 

 suggestion of this dispatch, Pogson searched, and found a 

 comet near the predicted spot, but was successful in observ- 

 ing it on only two days the second and third of December; 

 and for some time the impression seems to have prevailed 

 among astronomers that he must have actually observed 

 Biela's comet. His observations, however, have been care- 

 fully discussed by Oppolzer, and now recently more thor- 

 oughly by Bruhns. Oppolzer and Klinkerfues agree that 

 Pogson's comet was really in the most intimate connection 

 with the star shower, and possibly was really the head of 

 Biela's comet. Bruhns, however, seems conclusively to show 



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