Trigonometrical Survey. 4 99 
And those mean distances of St. Ann's Hill and Banstead, and 
Hind Head and Bagshot, with the 14 and 15th triangles (exclud- 
ing the 16 and 17th), will produce 36574,6, and 36574,9 respec- 
tively. 
Lastly; — if the computations are carried directly from one 
base to the other, independent of the mean distances and the 14 
and 1 5th triangles, the greatest and least results will be 36574,8, 
and 36573,8, the mean being 36574,3 feet, or about an inch 
short of the measurement. 
Of the several ways by which the base of verification, or dis- 
tance between Beacon Hill and Old Sarum is deduced, the first 
seems to have the preference, because the angles of the 6 and 7th 
triangles appear to have been observed very correctly. The re- 
sults from the 14 and 15th triangles cannot be considered as very 
conclusive, because the angle at Highclere is so acute that a 
trifling error in it will vary the distance from Beacon Hill to 
Thorney Down very considerably : and we had some reasons for 
being dissatisfied with this angle, and also that in the same tri- 
angle at Thorney Down, on account of the strain in the clamp. 
See Sect. ir. Art. vi. 
Although the result of this comparison might afford some 
reason for supposing, that the sides of the triangles in this 
branch would be sufficiently near the truth, were all of them 
computed from the base on Hounslow Heath, yet, to approach 
more nearly to their correct distances, those which are marked 
with asterisks, have been computed with each base, and a mean 
of the results taken. The remaining sides have been determined 
by the bases in their vicinity. 
