2 ^ 2 Gen. Roy’s Account of 
Steeple; SC the earth’s furface ; KO the horizontal line at 
right angles to KC ; and SL = CK. 
The diftance between Allington Knoll and Tenterden has by 
the triangles been found to be 61775.3 feet, which, allowing 
61234 fathoms = i° gives 10' 5". 3 for the length of the con- 
tained arc CS nearly. Half of this arc = f 2 ". 6 is the angle 
OKL, from which fubtra&ing the obferved angle of depreflion 
of T as feen from K = OKT = f 51", there remains the angle 
TKL=x 7 ii". 6, and confequently this angle will be fub- 
tended by 21.4 feet=LT, or what the top of the flag-ftaff at 
Tenterden would have been higher than the axis of the tele- 
fcope at the Knoll, if there had been no refraflion. 
But the top of the flag-ftaff on Tenterden fteeple was 3.1 
feet higher than the axis of the telefcope when the inftrument 
flood at that ftation ; therefore, 21.4 -3.1 = 1B.3 is what the 
axis at Tenterden would have been higher than the axis at the 
Knoll, if there had been no reflation. 
Again, let T (fig. 16.) be the place or the axis of the tele- 
fcope on Tenterden Steeple ; K the ground at the ftation on 
Allington Knoll ; TO the horizontal line ; and CL = ST . 
At the ftation T, the depreflion of the ground at K, or the 
angle OTK, was obferved 3' 55 / \ which being fubtra&ed from 
^ 2 // .6 = OTL = half the arc of diftance, there remains 
i v 27^.6 = the angle KTL. This laft angle, with the diftance 
between the ftation s, 61775.3 feet, give KL=26.3 feet, for 
what the ground at K would have been higher than the axis at 
Tenterden, if there had been no refra&ion. 
But the axis of the telefcope, when at the ftation K, 
was 5.5 feet above the ground; therefore, 26.3 + 5.5 = 31-8 is 
what the axis at the Knoll would be higher than the axis at 
Tenterden* 
1 
Hence 
