Additional Notc^. 407 



order to restore, as far as possible, the credit of lliat iiiveiuion to 

 our city, and to the posterity of Mr. Godtiey. How he came to 

 be deprived of it may be made a question by some. I answer that 

 Mr. Godfrey sent tiie instrument to he tried at sea by an accjuaint- 

 ance of his, an ingenious navigator, in a voyage to Jamaica, who 

 showed it to a captain of a ship there just goiii;,' tor Ew^lntid, by 

 which means it came to tlie knuw ledge of IMr. Hadk-y, though, 

 perhaps, without his being told the nnme of the real inventor. 

 This fact is sutiiciently knov/n to many seamen and others yet 

 alive in thi^ city ; and established beyond doubt by the followhig 

 letters, written about that time. It is, therefore, submitted to 

 the world whether, after perusing the letters, they ought not, in 

 justice, to call that instrument, for tlie future, Godfrey's, and no; 

 Hadley's, quadrant. 



To Dr. Edmuxd Halley *. 

 Esteemed Friend, 



The discovery of the longitude having, of late years, employed 

 the thoughts of many, and the world now expecting, from tliy 

 great sagacity and industry, some advances towards it, far exceed- 

 ing all former attempts, from the motion of the moon, to the 

 ascertaining of which thy labours have so long and happily been 

 directed ; the following notice, I hope, will neitlier be tirought 

 unseasonable nor prove unacceptable. That the success of this 

 method depends on linding the moon's true phice for cnie meri- 

 dian by calculation, and for another by observation, I think is 

 generally allowed 3 the first of which being depended on from tliy 

 great genius, what remains is some certain method for observa- 

 tion, practicable on that uncertain element the sea. In order to 

 tliis, thy predecessor at Grcemoich, if I mistake not, for some 

 years published his calculations for the UK.on's future appulse to 

 the fixed stars, which would save all observation but tliat of a 

 glass J but these not often happening, and the moon often ha\ing 

 a considerable parallax, when they did, that project dropped. 



For finding her place by taking her greater distances from stirs, 

 the fore-statf or cross-staff cannot be exact enough : and quadrants, 

 sextants, &c., with two telescopes, afe impracticable at sea. 



Dr. Biester's late proposal for taking the ditference of riglit 



* An Introductory paper winch I !»ave net transcribed, not tliinkJ;:g it im- 

 portant, mentions this letter as N° 435 in the >PWoj<>//j/.j/ 7'r^'/Ti..v//&//i, ard 

 f ntitlod an " Account of Mr. Thomas Godfrey 't Improvement of Davis's 

 Quadrant transfcirt-d to the Mariner's Bcnv. ' 



