[ S31 ] 
the bafe iiiRaiinoch. See Phil. Tranf. vol. LVIII. p. 3 1 3- 
324.and326. Hence, with the help of the angles taken 
with the theodolite at the ends of the bafe in Rannoch,. 
and at the Weft carn^ the horizontal diftance between 
the Eaft and Weft earns comes out 4047,4 feet. Nearly 
the fame refult comes out from the bafe meafured on 
the South fide of the hill, though with lefs exaeftnefs % 
this, when all correeftions are made, is 3011,684 feet,, 
whence the diftance of the two earns fhould come out 
4058 feet, or about ten feet longer than refults from the 
bafe in Rannoch. But I prefer the dedudfion from the 
bafe in Rannoch as moft to be depended on. Hence, by 
the calculation of the two triangles formed by the two- 
earns and the two Rations of the obfervatory, the diftance 
between the parallels of latitude palling through the two 
Rations comes out 4364,4 feet, which, according to 
bouguer’s table of the length of a degree in this latitude of 
5 6° 40', at the rate of 101,64 Engiifti feet to one fecond, 
// 
anfwers to an arc of the meridian of 42,94. The other 
feries of triangles carried acrofs the hill, gives the fame 
diftance of the parallels only lo feet lefs, and confe- 
quently the arc of 4 jie meridian only -j^th of a fecond 
lefs. Thus the difference of latitude found by the aftro- 
nomical obfervations, comes out greater than the differ- 
ence of latitude anfwering to the diftance of the parallels,. 
// //. 
the former being 54,6, the latter only 42,94* The 
// 
difference 1 1,6 is to be attributed to the fum of the two 
contrary attractions of the hill. 
The 
