■I 9 2 Roy’s Account of a 
of verification ; but \i Tatterlees-Bam*, or any other point on 
the range near it, can be feen from Ruckinge, then the Ra- 
tion on the knoll, as well as that at Lymne, will become 
equally unneceflary, and the triangle of verification will be- 
come Tenter den. Lid , Tatter lees. 
It will be perceived, that I propofe to have a Ration on 
Fair light Head , a land of confiderable height, from whence 
there is a good view of the coaR of France near Boulogne. 
From this point and Tatterlees, with the help of the Indian 
lights, I have no doubt of obtaining a fine interfe&ion of the 
lignal of the Boulemberg , a hill of fome note behind the town 
of Boulogne, and one of the Rations made ufe of by the 
French Academicians in the execution of their triangles. The 
advantages of obtaining a triangle of this magnitude, whofe 
tides are refpecbively in, length about 45, 36, and 25 miles, are 
too obvious to require any comment. 
The high chalk cliffs near FolkRone prevent Dover Cafle 
from being feen from Lid, or any where in the plain of 
Romney-marfh. Hence it will become neceflary to form two 
final 1 triangles to the northward of Tatterlees, in order to 
obtain an interfeftion of one of the turrets of the keep of that 
caRle. Of the center of the keep, it will be perceived, by the 
R ron g dotted lines, that the French Academicians have pro- 
cured, from their Rations at Calais , Blancnez , and Auding- 
hen , an acute interfeflion (de la Grojfe Tour de DouvresJ 
making in the whole an angle of 28° i6 / 20". 
The points which are obvioufly the beR for connecting our 
triangles with thofe of our neighbours, are the Boulemberg, 
Blancnez, and Calais, provided we could by any means obtain 
* Tatterlees Barn, in Packe’s Map of Eaft Kent, on the fummit of the 
chalk hills, 727 feet above thefea. 
as 
