and Longitude of the Royal Obfervatory at Greenwich. 
l S3 
THE preceding Memorial of the late M. Cassini de 
Thury was put into my hands by Sir Joseph Banks, our 
Prefident, on the 28th of April, 1785, defiring me at the 
fame time to give an anfwer to it. Happy if I can folve the 
doubts entertained by the late Royal Aftronomer of France 
concerning the latitude and longitude of this Royal Obferva- 
tory, and at the fame time do juftice to the memories of my 
learned predeceflors, and to myfelf, I fhall give an account 
of the principal Operations that have been performed here 
for afcertaining thofe points, and then add my own re- 
marks to elucidate the fubjeCt and reconcile the difficulties in 
queftion. 
Had Dr. Bradley lived longer, for the benefit of aftronomy, 
topublifh his valuable obfervations, or had they been fince pub- 
lifhed by another hand, which unfortunately they hitherto have 
not,thefe remarks might have been unneceffary, and perhaps even 
the occasion for them might never have occurred ; as it would 
have then appeared upon what foundation the latitude of this 
Obfervatory had been eftablifhed, and what differences of me- 
ridians between Greenwich and the other principal Obfervato- 
ries of Europe refulted from the obferved eclipfes of Jupiter's 
Satellites and other celeflial phenomena. 
However, having formerly been apprifed by Dr. Bradley 
himfelf of Several particulars of moment relative to his obfer- 
vations, and particularly of the method which he ufed for fettling 
his latitude and refractions, after he became poflefled of the 
new inftruments in 1750, and being aflifted with fome of his 
manufcript calculations, with the addition of my own obferva- 
tions, I flatter myfelf I can throw the light wanted on the 
Vol. LXXVII. X queflion. 
