ADDRESS. Xliii 



been recently observed in Biela's comet. This comet has a period of about 

 six years and a half, and has been observed a considerable number of times 

 on its periodical return to the neighbourhood of the sun. It appeared in 

 November 1845, and in the following January the phaenomenon alluded to 

 was observed for the first time. The comet had become divided into two 

 distinct parts with separate nuclei. Sometimes the one and sometimes the 

 other appeared the brighter till their final disappearance. The elements 

 of the orbits of these twin comets were calculated by Professor Plantamour, 

 from observations made at Geneva in 1845-46, assuming them to be unin- 

 fluenced by each other's attractions. The correctness of these elements 

 could only be determined on the next return of the comet, which took place 

 in the autumn of last year, one of the nuclei having been first seen by Signor 

 Secchi at Rome, on the 25th of August, and the other on the 15th of Sep- 

 tember. The subsequent observations made upon them show that the ele- 

 ments of the orbits, as previously calculated from the Geneva observations, 

 were far from exact. A complete discussion of all the observations which 

 have been made on these comets during their last and previous appearances, 

 is now in progress by Professor Hubbard, of the Washington Observatory. 

 The distance between the two nuclei was much increased on their last ap- 

 pearance. Judging from the apparent absence of all influence and sympathy 

 between these bodies, it would seem that their physical divorcement, though 

 without known precedent, is final and complete. 



Stellar astronomy continues to manifest a vigour and activity worthy of 

 the lofty interest which attaches to it. Bessel had made a survey of all stars 

 to those of the ninth magnitude inclusive, in a zone lying between 45° of 

 north and 15° of south declination. Argelander has extended this zone from 

 80° of north to 31° of south declination. It comprises more than 100,000 

 stars. Last year was published also the long-expected work of M. F. G. W. 

 Struve, containing a catalogue of stars observed by him at Dorpat, in the 

 years 1822-43. They are principally double and multiple stars, which had 

 been previously micrometrically observed by the same distinguished astro- 

 nomer. Their number amounts to 2874; the epoch of reduction is 1830. 

 The introduction contains the discussion of various important points in 

 stellar astronomy. 



Notices have been brought before us, from time to time, of the nebulae ob- 

 served through Lord Rosse's telescope. This noble instrument, so unrivalled 

 for observations of this kind, continues to be applied to the same purpose, 

 and to add yearly to our knowledge of the remotest regions of space into 

 which the eye of man has been able to penetrate. Almost every new obser- 

 vation appears to confirm the fact of that curious tendency to a spiral arrange- 

 ment in these nebulous masses, of which mention has so frequently been made. 

 To those persons, however, who have neither seen the objects themselves, nor 

 careful drawings of t':em, a mere verbal description must convey very indi- 

 stinct conceptions of the spiral forms which they assume. I have therefore 

 had the drawings made, which are suspended in the room for your inspection. 

 They will convey to you at once an idea of the spiral forms alluded to. I am 

 indebted to the kindness of Lord Rosse for the use of the original drawings, 

 and for these large and accurate copies of them to our excellent Secretary, 

 Mr. Phillips, who, with his usual ready activity in the cause of the Associa- 

 tion, has had them prepared for the purpose of this evening. Most of them 

 are representations of nebulas which have been very recently observed. 



Two pairs of these are respectively drawings of the same object, the larger 

 one of each pair representing the nebula as seen through the large telescope, 



