ef the 'Trigonometrical Operation * 5^5 
companion feems lefs liable to objection than that by a fingle 
correction of the fame angles* Accordingly, if we vary the 
angles (in reducing them to i Sop from Hounllow Heath to the 
XIII triangle, fo as to produce the greateft and leaft effects on 
the lengths of the oppofite ftdes, there will refute 141750! 
and 1 41 746I feet, nearly, for the greateft and leaft, and 
1417481 for the mean diftance of Fail light and Holiingborn. 
In like manner, the bafe on Romney Marfli will give' 
141745.6 and 141744*4 feet, nearly, and the mean 141745 
feet, for the diftance of the fame ftafions ; the difference in 
the mean refults is 5! feet on a diftance of near 27 miles; 
and therefore the bafe on Hoimfiow Heath meafures the other* 
by thefe determinations, to about 9 inches ; and, becaufe the 
latter bafe is the longeft, it would meafure the former on 
Hounflow Heath to fo me thing lefs. 
The diftance of the ftations of Fanlight and Holiingborn in 
the XIII triangle is 141747.1 feet, and from this all the dif- 
tances to the eaftward are computed ; but if the bafes are mea- 
fured equally exaCt, the diftance of the above ftations, or 
141745 feet, determined from the bafe on Romney Marlh, 
mu ft be more correCt than the other, becaufe the connection of 
Fairlight and Holiingborn with this bafe is formed by three or 
four triangles only, whereas on the other fide* the computation 
runs through eight or nine. The difference, however, is but 
2 feet, and that in an extent of almoft 27 miles, which will 
< ' 
make about 7! feet lefs for the diftance between the meridians 
of Greenwich and Paris. 
Among the angles corrected for computation, it will be per- 
ceived, that fometimes the quantity of an angle feems not to 
be exaCtly what the obferved angle ought to give. In thefe 
cafes the obferved angle is lefs to be depended on than the 
4 H % others 
