73 



PROCEEDINGS 



ROYAL SOCIETY OF EDINBURGH. 



VOL. III. 1851-52. No. 42. 



Sixty-Ninth Session. 



Monday, \st December 1851. 



Dr CHRTSTISON, Vice-President, in the Chair. 



The following Communications were read : — 



1. On the Total Eclipse of the Sun on 28th July 1851, ob- 

 served at Goteborg ; with a description of a new Position 

 Micrometer. By William Swan, Esq. 



I observed the eclipse from a hill about a mile to the north of 

 Goteborg, situated in latitude 57° 43' 6", longitude C' 47™ 49^, in 

 company with Mr Edward Lane, Advocate, who kindly rendered me 

 his valuable assistance in making the observations for time. Tlie 

 telescope I used was furnished by Mr Adie of Edinburgh. It has 

 a good object-glass, with an aperture of 2"1 inches, and about 315 

 inches focal length ; and the eye-piece employed in observing the 

 eclipse magnified about 28 times. A dark glass, lent me by Professor 

 Chevallier, consisting of a colotu'ed prism achromatized by a prism 

 of colourless glass, slid in a groove before the eye-piece, so as to 

 admit of being instantly removed. This glass made the sun's image 

 appear yellow, slightly tinged with green. 



As considerable discrepancies occur in the positions assigned by 

 different observers to the prominences seen at the eclipse of 1842, 



VOL. in. o 



