[ 5^3 ] 
on them, truly level, and in the true direcflion of the bafe. 
In order to fet the poles continually in the proper direc- 
tion of the bafe, the following method was ufed. The 
theodolite was firft fet up at one end of the bafe, and an 
upright pole at the other, and another in the middle, and 
a third was from time to time advanced to a little diftance 
forward ; and themeafuring poles were fometimes placed 
in the proper direction by the eye, looking along the 
lengths of both poles together to the upright pole before 
them, and fometimes by the help of the theodolite. In 
this manner, about the middle of September, a bafe was 
meafured by Mr. burrow and Mr. menzies of 3012 
feet, in the valley at the foot of the hill to the South- 
well: ; but not fo accurately as this method is capable of, 
owing to the Hands being very unfteady, through the 
loofenefs of the fpikes in the feet and other faults, during 
the meafuring the firft quarter of the bafe, though they 
were mended before the menfuration of the remainder 
of it. The menfuration of another bafe of the length 
of 5897 feet, in the meadow of Rannock, about 2 - miles 
to the South-weft of the centre of the hill, which I at- 
tended myfelf, was performed with the greateft accu- 
racy, according to the fame method, on the loth, i ith, 
and 1 2th of Odfober, with new Hands, more fubHantial 
and firm than the former. 
The extreme badnefs of the weather no lefs retarded 
the operations of the furvey than the celeHial obfer- 
vations; for there was almoH conHant rain, miH, or 
high wind, to obHru(H the ufe of the theodolite : indeed 
all 
