Royal Astronomical Society. 147 



He concludes by observing, that as the machinery is simple, by 

 no means expensive, can be made by an ordinary workman, is adapted 

 to all the engines now in existence which are moved by an endless 

 screw, as it lessens the labour of the artist and increases the accuracy 

 of the graduated instrument, he trusts his communication will prove 

 acceptable to all who are interested about such matters. 



II. Recomputation of Roy's Triangulation for connecting the 

 Observatories of Greenwich and Paris. By W. Galbraith, Esq. 



The author considers from internal evidence that Roy's measure- 

 ment of the base on Hounslow Heath was in his own scale, and that 

 of Mudge in Ramsden's scale, and he has used in his calculations 

 the mean of these in imperial measure, reduced to the mean level of 

 the sea. He has also availed himself of the New Survey of France 

 to obtain such data as it afforded to connect the two countries. 



Some of the most important of the results are as follows : — As- 

 suming the latitude of Greenwich to be 51° 28' 38"*50 N., and the 

 compression of the earth to be ^q, there results for 



Calais Lat. 50° 57' 27"*67 N. ; Long. 1°51' 17"*30 E. 

 Dunkirk Lat. 51 2 6 -68 N. ; Long. 2 22 39 '72 E. 



I Again, assuming from the new Description Geometrique de la France, 

 the long, of Calais to be 29' 0"*40 West of Paris, and that of Dun- 

 kirk 2' 22*"66 East of Paris, h m ■ 

 The long, of Paris by comparison with Dunkirk is 2 20 17*70 E. 



Calais 2 20 17-06 



Calais, from Kater's New Survey 2 20 19- 13 



h m s 



The Mean of which in Time is 9 21*20 E, 



Mr. Dent's Result by Chronometers was 9 21*21 

 And Sir J. Herschel's by five signals. . . 9 21*46 



III. Occultations of Fixed Stars and the Planet Jupiter by the 

 Moon. Observed at Hamburgh by C. Rumker, Esq. These will be 

 found in the Monthly Notices of the Society, vol. v. p. 293. 



IV. The following communications concerning the Great Comet 

 of 1843*:^- 



1 . Notes on its Appearance made during a Voyage from the Cape 

 of Good Hope to England. By M. Close, Esq., Commander of the 

 Ship Ellenborough. 



It was first seen on the evening of the 4th of March, and before 

 the discovery of the nucleus on the same evening was taken for a 

 lunar iris. The nucleus was on this evening estimated to be of equal 

 brightness with a star of the second or third magnitude, and the 

 length of its tail 32° 30'. The tail had a darkish line from its nu- 

 cleus through the centre to the end. Stars of the third magnitude 

 were visible through the broadest part, but not near the nucleus. It 

 was seen on several evenings, the last time being on the evening of 

 the 31st of March ; it was occasionally brilliant enough to throw a 

 strong light on the sea. The greatest length of tail estimated was 

 on the 19th of March, it being then 43° 30', and it was observed to 



* See also p. 54 of the present, and p. 323 of the preceding vol. — Edit. 



L2 



