60

CALCULATIONS TO ASCERTAIN THE TRACT 26.

Having now obtained the sums of the sines for the severalquadrants, the next business is to collect them together, anddeduct the negatives from the affirmatives. Now this maybe done either for each observatory separately, or for bothtogether. It is here done separately, in order from thenceto discover also the ratio of their effects.

And first for the Southern observatory o.

Affirmatives.

1 ..24-795 N.W.| A]t>

2 . . 19-792 N.E. )

7 . . 24-806 S.w. 1

8 . . 29-213 s.E. ) ep '

Negatives.

3 .. 2-374 s.W. ) Ak>

4 . . 0-375 s.E. )

5 . . 13-534 N.w. 1 D •

6 . . 12 356 N.E. j' Uep *

98-606 = sum of affirm. 28 - 639 sum.28-639 = sum of negat.

69"967 = effective sum of the sines for o.Secondly, for the Northern observatory p.

Affirmatives.

11 . . 25-078 s.w. A j t

12 . . 20-261 s.E. 5

13 . . 25-637 N.W. 2 p.

5- Dep,

14 . . 26-161 N.E. 3

Negatives.

9 . . 0-019 N.W. ? A1 k10 . . 0-090 N.E. 3

15 . . 2-774 s.w. ? D

16 . . 5-610 s.E. 3

97-137 = sum of affirm. 8'493 sum.

8-493 = sum of negat.

88-644 = effective sum of the sines for p.

69"967 = the same for o.

158-611 = the sum of the sines for both observ.

From these numbers it appears, that the effect of the attrac-tion at the Northern observatory is to that at the Southernone, nearly as 70 is to 89, or as 7 to 9 nearly. This differ-ence is to be attributed chiefly to the effect of the hills on theSouth of the Southern observatory, which were considerablylarger and nearer to it, than those on the back of the North-ern observatory. For though the Southern observatory wasplaced 273 feet above the level of the Northern one, whichremoved it considerably more above the centre of gravity ofthe hill than the latter, it was at the same time placed consi-