374 
Mr. Playfair’s Account of a 
by Dr. Hutton, is found = (2474.389) O -f (150. 855) M, 
which, added to the preceding, gives the whole attraction on 
the plummet at O = (5782.104) Q — (1903.209) M. 
The same quantities calculated for P, the north observatory, 
are (8061.022) Q — (3127.05) M. To which adding the 
attraction just found for O, we have (13843.126)0 — 
(5030.214) M “ the total force of attraction increasing the 
convergency of the plumb line on opposite sides of the 
mountain. 
Now if D be the mean density of the globe, it follows from 
Dr. Hutton’s calculations that 8“52272o x D is the measure 
of the attraction of the whole earth. But the Astronomer Royal 
having found by his observations, that the sum of the devia- 
tions of the plumb line on opposite sides of the mountain is 
11.6 seconds, the attraction of the earth is therefore to the sum 
of the opposite attractions of Schehallien, us radius to the tan- 
gent of 1 1 n .6, that is as 1 to .000056239, or as 17781 to 1 ; or, 
making an allowance for the centrifugal force arising from the 
earth’s rotation, as 17804 to 1. Therefore 17804: 1 1:87522720 
xD : (13843.126) Q — (5030.214) M, so that D = 
(13843,126) O — (5030.214) M, and hence D — 
3843 1,6 x Q-- 5°32H4 _xM d = ( S . 8l6 ) o - (1.023) M. 
If we suppose O = 2.639876 and M = 2.81039, as in the 
table above, D == 4 55886. 
Dr. Hutton makes D = ~~ multiplied into 2.5, the sup- 
posed density of the rock,* which gives D = 4.481, consider- 
ably less than the preceding. If in the formula D = (2.816) 
Q — ( 1.023) M we make Q = M = 2.5, the result should 
® Phil. Trans. Vol. LXVIII. p. 781. 
