[ m 1 



On the METHOD o/^ D E T ERMI N ING the LON- 

 GITUDE, by OBSERVATIONS of the MERI- 

 DIAN PASSAGES of the MOON and a STAR 

 made at two Places By the Rev. JAMES ARCHIBALD 

 HAMILTON, D.D. Profefor of Aflronomy at Armagh. 



General Rule for determining the ejlimate difference of the Longi- ^^^^ ^°^" '' 

 tilde of a given place., from fome well known meridian, by 

 ohfervations of the different intervals of A. R. of the moons 

 enlightened limb from a far at each place on the fame day. 



J-i E T the pafTage of the moon's enlightened limb be carefully 

 obfcrved to the neareft tenth of a fecond, over the feveral wires 

 of the tranfit inftrument, and let its pafTage over the centre be 

 deduced by taking a mean of its paffages over the equidiftant 

 wires, properly reduced. Let one or more fixed ftars that lie near 

 her parallel of declination, and alfo as near to her in A. R. as can 

 conveniently be had, be obferved in like manner. Let the rate 

 of the fydereal clock, which is the moft convenient for this 

 purpofe, be carefully afcertained, and from this and the obfer- 

 vations colled the exad difference of the moon's A. R. from 

 Vol. VI. B b one 



