392 Proceedings of Philosophical Societies. [May, 



On one of the principal islands of this group, the mineral, known 

 by the name of pargasite, is fomid in one or more large veins of 

 white primitive limestone which traverse the island from side to 

 side, and which seem to bear some analogy with respect to their 

 geological situation, and their external characters, to the lime- 

 stone of the Hebrides, especially in the Isle of Tirey. The 

 country through which this limestone passes is gneiss, the 

 fissures of which are in a direction parallel to the course of the 

 vein. The breadth of the vein varies from 20 to 100 feet. 



ASTRONOMICAL SOCIETY. 



April \3, — A paper, from Mons. Nicollet, of the Royal Obser- 

 vatory at Paris (communicated by the Foreign Secretary), was 

 read this evening : it contains his own calculations of the 

 elements of the comet lately discovered by him in the Constella- 

 tion Pegasus ; they are as follows, viz. 



Perihelion passage, March 21 9° 33' 7'' Paris time 



Perihelion distance 0-091113 



Log. Perihel. dist 8-9595327 



Longitude of ascending node 48° 32' 12'' 



Longitude of perihehon (on the orbit) 239 18 37 



Inchnation of the orbit 74 10 53 



Motion retrograde. 



A paper likewise on the same subject, transmitted to the 

 Society by Dr. Olbers, one of its associates, was read ; it con- 

 tained the following elements calculated by Professor Encke, of 

 Seeberg, by Professor Nicolai, ofManheim, and by Mons. Von 

 Staudt, of Gottingen. 



Perihel. passage . . 



Long, of perihel. . . 

 Log. perihel. dist. . 

 Long, ascend. node 

 Inclination of orbit. 



Prof. Nicolai. 



Mar. 21. 6016 



M.T.Manheim 



239° 34' 5" 



8-96466 



48 43 34 



73 23 15 



M. \'on Staudt. 



Mar. 21,6026 



M.T. Gotting. 



239° 36' 0" 



8-9(i4l627 



48 45 44 



73 16 33 



Motion retrograde. 



In this paper also allusion is made to the anomalous appear- 

 ance lately observed on the moon's disc, of which it will be 

 remembered that an account was presented to the Royal Society 

 by our countryman Capt. Kater. The Doctor, however, differs 

 from the British philosopher as to the cause of the phencmenon, 

 and does not consider it volcanic. 



A Description of an improved Repeating instrument, by 

 Qeorge DoUond, FRS. and member of this Society, was then 



