Lithological Survey of Schehallien. 375 
agree with Dr. Hutton’s, and does so very nearly, making 
D = 4.482. 
In all this, we have proceeded on the supposition that the 
granular quartz not only constitutes the summit of the moun- 
tain, or the part above the level of the observatories, but that 
it also descends into the interior of the mountain down to its 
base, where it is bounded by the curve line abe (Fig. 1 ). On 
the other supposition mentioned above, that the granular 
quartz does not constitute the interior nucleus of the moun- 
tain, but is confined to the upper part of it, the rest consisting 
of micaceous schistus, our formula, after undergoing certain 
changes, may also be accommodated to this hypothesis. In 
the value of the attraction of the part of the mountain below 
O, viz. (3307.715)9 — (i753-»54) M > we must suppose 
Q = M, when the above quantity becomes (1554.561,) M. 
To this we are to add T, or the attraction of the part of the 
mountain above O, which remains the same as before, viz. 
(2474.389) Q — (150-055) M, to which if we add (1554.5-61) 
M, the sum (2474.389) Q -|- (1404.506) M is the whole 
attraction on the plummet at O, according to this new hypo- 
thesis. 
If the same changes are made with respect to the observa- 
tory P, we shall have the total attraction. Now the attraction 
of the part of the mountain below P = ( 5593.347 ) O — 
(3172.15) M, which if Q = M becomes (2421.197) M. Also 
the attraction of the part above P is (2407.675) Q + (45.15) 
M. If to this be added (2421.197) M the amount, or 
(2467.675) Q -j- (2466.347) M is the total attraction on the 
plummet at P. 
To the total attraction at O = (2474.389) O -j- (14040.506) 
