Trigonometrical Survey. 505 
No 
Triangles. 
Observed 
ang.es cor. 
Distances of the stations from 
the intersected objects. 
St. Buryan - 
Pertinney - 
Windmill in St. Mary’s 
8 °3 2 4 53 
92 2 6 33 
V Windmill in St. J 
J Mary’s - \ 
Feet. 
172183 
171203 
3 *5 
St. Buryan 
Pertinney - 
Flagstaff of the fort 
in St. Mary’s 
82 8 18 
93 47 18 
1 Flagstaff in St. f 
j Mary’s - f 
17489O 
173626 
The distance from the Day-Mark to Karnminnis, as obtained from 
the 309th triangle, is 190985 feet, and by the 310th, 190989 feet, 
which differs only 4 feet from the former; and by the 310th and 
311th triangles, the difference of the distances from the same ob- 
ject, to the station on Pertinney, is 17 feet; which, allowing for 
the shortness of the bases, must be considered as trifling. We 
may presume, therefore, that had not the Day-Mark been seen 
from Karnminnis, but from Sennen and Pertinney alone, the obser- 
vations from which the angles of the 311th triangle are derived, 
would have afforded the means of computing the distance with suf- 
ficient precision. In like manner the 312th and 313th triangles seem 
to prove, that the observations made to St. Agnes’ Light-house were 
sufficiently accurate, as there is a difference only of 16 feet between 
the distances of the Light-house from Pertinney. The ball on the 
top of the Light-house was the object always observed; and the 
Day-Mark being pyramidical, we had the means of making the ob- 
servations at the different stations to the same point of this building. 
