422 Major -Gen era! Roy’s Account of the 
the farther extremity; on the 2ad of June, the tranfit inftru- 
ment was adjufted over the thirteenth picket at Han worth 
Summer- houfe, while directed upon the fiag-ftaft. But it being 
now found, that the vertical plane palling through the flag-ftafF 
fell to the eaftward of the center of Banfted Spire, therefore 
the trail fit was gradually moved to the eaftward, until by 
repeated trials the three points were perceived to be in the fame 
vertical plane, when the picket was moved, and re-placed 
exadtly under the axis of the telefcope, a few inches from its 
firft pofition. The fame operation was repeated at the twenty- 
ftxth ftation, on the farther bank of the Staines Road ; and, 
laftly, at the forty-fixth, forming the north- weft extremity of 
the bafe ; where a pit was immediately dug for the wheel, 
which was placed therein, wfithout however filling in the earth 
for the prefent, that being deferred till near the completion 
of the meafurement with the deal rods. Thus the two extre- 
mities, and two intermediate points of the bafe, being accu- 
rately placed, by the help of the tranfit inftrument, in the 
fame vertical plane with Banfted Spire, it was eafily feen, that 
by arranging camp colours in the intervals at any time, all the 
other points might be brought fo nearly to coincide with thefe 
firft, as not to occafion, by deviation, any fenfible error in the 
meafurement afterwards to be made. This application of the 
tranfit (hewed us, however, that fome labour had been loft by 
not ufing it fooner : for at the Staines Road, the tract cleared 
by the foldiers deviated about two feet and a half too much to 
the weft ward for the true line ; and at King’s Arbour it was 
twice as much ; fo that we w r ere now obliged to widen the 
cleared tract, by adding to the eaftern fide of it. 
On the fame day that the chief points in the bafe were fixed 
by means of the tranfit, and the levels of the third fedtion 
taken 
