and Longitude of the Royal Obfervatory at Greenwich. 1 6 <) 
His own observations in 17^8, after examining and 
making an allowance for the error of the total arc of 
his quadrant - - - - 48 50 14 
His further observations in 1 740, making allow- 
ance for the error of the total arc of his quadrant, 
and conlidering the effect of the Hate of the air indi- 
cated by the thermometer upon the refraCtions 48 50 r <; 
In the Memoires of the Royal Academy of Sciences 
for 1744, M. Cassini deThury (the author of the 
memoir) finds from his own obfervations, with the 
fame refractions - - - - 48 50 12 
In the Memoires of 1755? the Abbe de la Caille^ 
from a nice and accurate calculation of his obferva- 
tions made at the College of Mazarine, at Paris, and 
the Cape of Good Hope, deduces new tables of re- 
fraction fuitable to each place, and Hates their re- 
fpeCtive latitudes, and thence that of the Royal Ob- 
fervatory at Paris - - - 48 50 14. 
Hence the ancient obfervations of M. Picard, M. 
de la Hire, and the Chevalier de Louville give 48 50 10 
The modem and more accurate obfervations of M. 
Maraldi, M. le Monnier, M. Cassini de 
Thury, and the Abbe de la Caille, give - 48 50 14; 
which is now generally made ufe of by the French aftronomers 
as the true latitude of their Royal Obfervatory ; and from the 
near agreement of io many diligent obfervers and able aftrono- 
mers cannot be fuppofed to differ above 2 or f' from the truth. 
The difference of this and 51° 28' 40 /r , the latitude or the 
Royal Obfervatory at Greenwich above ftated, is 2 0 38' 26 , 
the true difference of latitude of the two Obfervatories, which, 
Vo l. LXXVIL Z fl0in 
