778 Mr. hutton’s Calculations to afcertain 
From thefe numbers it appears, that the effect of the 
attra&ion at the Northern obfervatory is to that at the 
Southern one, nearly as 70 is to 89, or as 7 to 9 nearly- 
This difference is to be attributed chiefly to the effect of 
the hills on the South of the Southern obfervatory, which 
were confiderably greater and nearer to it than thofe on 
the back of the Northern obfervatory. For although the 
Southern obfervatory was placed 273 feet above the level 
of the Northern one, which removed it confiderably 
more above the center of gravity of the hill than the lat- 
ter was, it was at the fame time placed confiderably 
nearer than the other to the middle in a horizontal direc- 
tion ; fo that probably the one difference nearly balances 
the other; and accordingly we find that the fum of the 
affirmative altitudes for o is 44*587, and of thofe for p- 
45*339, which differ by only a 45th part nearly. 
It only remains now to multiply the fum of the fines 
by the common breadth of the rings, and by the common 
difference of the fines of the angles made by the meri- 
dian and the feveral radii. It has already been ohferved,, 
that the former is 666|, and the latter therefore 
T V x 666 j = *-222 =• 122 is their product : consequently,, 
158*611 x 5 -2?=88iij nearly, is the fum of the two op- 
pofite attractions made by the hill, See. at the two obfer- 
vatories,. 
