the Trigonometrical Operation . 
' |kv a 'J •" & i. w * it? ■ ' i 
Feet, 
From infpe&ion of the table it will appear, 
that the total apparent length of the bafe, as 
given direaiy by the Reel chain, was 95 1 2 AVA 
yards; which are equal to 28536 
But when the new points, at the diftance of 
twenty-five feet from each other, were laid off 
on the chain in Mr. Ramsden’s Ihop from the 
original points on the great plank of New-Eng- 
land deal, the temperature was 55°, that is, 7 0 
below 62°; wherefore the contraction of the 
chain by i° of Fahrenheit being =0.00763 in. 
this x 7 0 x 285.37 chains = 1 5.242 in. is the 
reduction for the total contraction below 62°, 
to be taken from the apparent length ; which are 
equal to * " 30 1 
The apparent length is likewife to be leflened 
by the excefs of the corrections with the fign — 
above thofe with the fign + in the annexed table | 
becaufe the temperature of the chain, when ac- 
tually applied to the meafurement, being fo much 
below 62°, the apparent length became thereby 
too great by 30.65 inches, which are equal to 2 
To be deduced alfo from the apparent length, 
the reduction on two hypothenufal diftances, 
meafured at the Ruckinge extremity of the bafe, 
which is fuddenly elevated above the lowed part 
fifteen feet, amounting to 0 
The fum of thefe three reductions, to be taken 
from the apparent length, amounts to - 4 
S 2 
131 
In. Pts. 
8-835 
3.242 
6.6s 
3.023 
0.915 
And 
