Meafurement of a Bafe on Hounflow-Heath. 417 
the third, we found ourfelves, on the 1 6th of June, in readi- 
nefs to begin the rough meafurement. 
Lieut. Colonel Calderwood, of his Majefty’s Horfe- 
Guards, F.R.S. had, from the beginning, been fo good as 
to promife his aftiftance in the operation. Lieut. Colonel Prin- 
gle too, of the Corps of Engineers, obligingly became a 
volunteer on the occafion ; as did alfo Mr. Lloyd, F.R.S. a 
few days afterwards ; while Enfign Reynolds, of the 34th 
regiment, who had for fome time paft been employed in fur- 
veying the environs of the Heath, continued that work with 
fuch fpare hands as could be afforded him for that purpofe; 
and it is to the plan (tab. XVI.) done by that officer, that it will 
be neceffary to refer in any thing regarding locality, in what 
has hitherto been faid, as well as in the fubfequent relation. 
The lower end of the bafe had for fome time paft been dift 
tinguiffied by a St. George's flag fixed to the top of a fir fpar* 
thirty- five feet in height; and one of the fignal bell-tents ftill 
remained at the ftation near the fummer-houfe. A rope of 
200 yards being made very faft by a ftrong iron picket, driven 
into the ground at the bottom of the flag-ftaff, the other end 
was carried on along the bafe, and placed at the bottom of a 
camp-colour, in a line with the bell-tent. The rope being 
wound around a ftrong iron reel, prepared for the purpofe, was 
thereby ftretched extremely tight, a perfon occafionally lifting it 
up in the middle, or at other places, and letting it drop again, fo 
as to bring the whole into the fame ftraight line. Five perfons 
were neceffary for the proper management of the chain; two 
at each end for its adjuftment there, and one towards the mid- 
dle, to lay it clofe to the rope, or to bear it up in any particu- 
lar place, where the circumftances of the ground rendered 
fuch precautions ufefuk The zero or rear end of the chain 
I i i 2 being 
