454 
The Account of a 
“ approximate value of d a, will give the correct value of d a. 
“If the third part comes out considerable, it should be com- 
“ puted anew with the last value of d a. The value of d a, 
“ finally corrected, applied to a, will give A, the angle between 
“ the chords.” 
In the application of the above rule, to the computation of 
such corrections as may be applied to the angles of any tri- 
angles in this survey, it is manifest that the last step may be 
entirely neglected on account of the smallness of the approxi- 
mate value of d a, whose versed sine is one of the arguments. 
Being, therefore, confined to the use of the two first steps,' the 
operation is very short. An example is here given in the com- 
putation of the correction for reducing the angle at Chancton- 
bury Ring in the 39th triangle, given in the last account (see 
Phil. Trans, for 1795, p. 492), to that formed by the chords. 
EXAMPLE. 
Constant logarithm - - 5,0134 ----- 5,0134 
Log. tang. \ a — 78° 56' - 10,7112 Log. co. tang. £ a - - 9,2887 
Log.vs .f . H + b-19' 5 3", 5 5,2237 Log.ws. £ H-A = 5' 53",5 4> l66 9 
0,9483 + .8", 8 8 — 2,4690 + o",03 
1 st correction — 8 ,88 
2d correction -f 0,03 
— 8,85 the correction required. 
