Trigonometrical Survey. 
U 1 
SECTION SECOND. 
Containing Particulars relative to the Commencement of the Tri- 
gonometrical Operation. — An Account of the Improvements in 
the great Theodolite ; and a Relation of the Progress made 
in the Survey in 1792, 1793, and 1794, together with the 
Angles taken in those Tears. 
art. 1. Of Particulars relative to the Commencement of the Tri- 
gonometrical Operation. 
Having, by the re-measurement of the base on Hounslow 
Heath, sufficiently determined its accuracy, it became neces- 
sary, upon the approach of the following spring, to form some 
plan which might enable us to commence the survey with the 
most advantage. 
Of those which were suggested, that of proceeding imme- 
diately to the southward with a series of triangles seemed the 
most eligible, not only because, in the first instance, the execu- 
tion of it would forward one great design of the business, in 
an early determination of some principal points upon the sea- 
coast, but also because a junction of the eastern part of the 
series with that of the western of General Roy, would afford an 
early proof of what degree of accuracy had attended both ope- 
rations. 
To ascertain the truth of the General's work, by verifying 
some principal distance or distances, was an object which pre- 
sented itself, not only as interesting and curious, but as highly 
necessary, in order to determine whether, by the result, the 
triangles might stand good, and become a part of the general 
series. 
