41 6 Major-General Roy’s Account of the 
lids ; one a femi- circle, with the central point marked by a 
line cut on its diameter, brought into the direction of the bafe ; 
with which line the gilt wire, fufpended at the extremity of 
the firft rod, was made to coincide on the commencement of 
the meafurement. The other lid has a very fmall hole made 
in its center, through which the plummet wire is to pafs, 
when fufpended from the center of the inftrument, hereafter to 
be made life of for the determination of the angles at the bafe, 
or in any other ftation whatever, where it may be neceftary to 
bring it very accurately over a point on the furface of the 
ground underneath. 
Rough meafurement of the Bafe with the Chain , and determina- 
tion of the relative heights of the Stations by means of the 
Lelefcopic Spirit Level Tab. XVI. and XVII. 
Having in the preceding defcription of the various inftru- 
ments, originally provided for the meafurement of the bafe, 
fully explained their conftrudions, ufes, and modes of appli- 
cation ; and having thereby anticipated, in a great degree, 
what muff otherwife have been faid to make them underftood 
in any account, blended with that of the execution ; little 
more now remains to be given than the journal of our pro- 
ceedings from day to day, and the ultimate refult of the ope- 
ration. 
After a very tedious delay, Mr. Ramsden having at lafh 
produced his hundred- feet chain, with the portable tranlit inftru- 
ment ; and having lent us an excellent telefcopic fpirit level, 
for determining the relative heights; two fedions of the bafe 
being likewife cleared by the foldiers, and fome progrefs made in 
