and Langitude of the Royal Obfervatory at Greenwich. 177 
with a 6-feet mural quadrant of Bird’s conftru&ion, cor- 
refpondent to. the fame obferved by himfelf, I fhall make fome 
remarks on this comparifon, becaufe it appears to me to afford 
a ftrong argument to fhew that the Abbe de la Caille’s re- 
fractions are too great; and that Mayer’s, which agree with 
Dr. Bradley’s, are juft. The Abbe, after correcting the 
zenith diftances of 22 ftars obferved at both places by his own 
table of refraCtions, finds the difference of latitude of Gottin- 
gen and Paris, by a mean, to be 2 0 40' 35", 1? which added 
to 48° 5 1' 29^,3, the latitude of the College of Mazarine? 
gives.him the latitude of M. Mayer’s Obfervatory 32' 4", 4. 
He adds, that fome obfervations of the pole ftar fent to him 
by M. Mayer would give the latitude of Gottingen \f' lefs 
than he has eftablifhed it, as juft mentioned. Now I find, 
that if M. Mayer’s obfervations of the pole ftar, as well as of 
the ftars to the fouth of the zenith, be corrected by M. 
Mayer’s table of refractions, and the Abbe de la Caille’s 
obfervations by his table of refractions, the latitude refulting 
from M. Mayer’s obfervations of the pole ftar will agree to 
2" with that refulting from the difference of latitude by the 
ftars to the fouth; for fubtracting 19" from 51 0 32' 4^,4, the 
latitude which the Abbe de la caille has afligned to .Got- 
tingen in the manner above-mentioned, there remains 51 0 31' 
45", 4 the latitude which he found by the pole ftar; to which 
adding 5 8, the refraClion at the mean height of the pole 
ftar according to the Abbe de la Caille, the fum 51 0 32' 
38", 2 muft be the apparent height of the pole by Mr. Mayer’s 
obfervations, which diminifhed by 45^,6 , M. Mayer’s re- 
fraClion, gives the true latitude of M. Mayer’s Obfervatory 
51 0 3C 52", 6. But by the difference of the Abbe de la 
Caille’s and M. Mayer’s zenith diftances of the 22 ftars to 
Vol. LXXV 1 I. A a the 
