1818.] Annular Eclipse of the Sun. 183 



Sun's semidiameter 0' 00° 15' 54-8" 



horizontal parallax 00 00 8-7 



declination (north) 5 59 41-0 



From these elements it may be determined that the moon's 

 shadow first touches the earth's disc at ll h 23' a.m. apparent 

 time at Greenwich, in N. lat. 59° 43', W. long. 90° 50' ; * 

 and that it finally leaves it at 4 h 39^' p.m. apparent time at 

 Greenwich in N. lat. 3° 21', E. long. 20° 25'. Consequently the 

 total duration of the general eclipse to the inhabitants of the 

 earth will be about 5 h 17'; but at no one place in particular will 

 the duration be much more than half that time. 



The central path of the moon's shadow across the earth's disc, 

 which is the most material circumstance in inquiries of this 

 nature (since it serves to point out those parts of the world 

 where the eclipse will be seen annular), may be determined with 

 considerable accuracy from the principles laid down by M. 

 Delambre in his " Traite d'Astronomie " (vol. ii. p. 384) ; and, 

 agreeably to the formulas which he has there given, I have 

 carefully computed the following table, which shows the several 

 points (expressed by positions of latitude and longitude) through 

 which the centre of the moon's shadow will pass in its progress 

 across the earth's disc at the several times therein mentioned. 

 The first column denotes the apparent time at Greenwich at the 

 moment when the centre of the moon's shadow passes the given 

 points laid down in the second and third columns, and the last 

 column shows the corresponding apparent time at those places. 



From this table it will be seen that the central eclipse com- 

 mences in N. lat. 81° 39' 29", W. long. 149° 32' 55", when the 

 sun and moon will rise together (the centre of the moon being 



• AH the longitude! in this memoir are reckoned from the mcridiau of Green u ich. 



