34 
[No. 1, 
The Trigonometrical Survey of India. 
A table of the resulting elements is given, together with a memoran¬ 
dum specifying the mountains which could be identified as having been 
previously observed by other surveyors. J- T. W. 
Of the Secondary Mountain Triangulation. 
57. The magnitude of the triangles for determining the positions 
of the hill peaks, and other unavoidable peculiarities attendant on 
the operations in general, have necessitated some few departures from 
ordinary precedents in the performance of the required calculations. 
These may be briefly noticed. 
58. Identification. —The primary difficulty which the computer 
meets with is, in the identification of the numerous points whose 
positions have been determined. Observed by different persons, after 
long intervals or from different points of view under the disadvan¬ 
tages of altered aspects, the same hill will be found noted in the 
angle books under various characteristics. For instance, Mont 
Everest was called v by Colonel Waugh, n by Mr. Nicolson and b by 
Mr. Armstrong, while the peak XXXVIII. is named id at one sta¬ 
tion of observation, n 3 at another and “ I west peak” at a third, by 
the same observer. This plurality of characteristics, under the 
circumstances, is clearly unavoidable. It remains to state how the 
required identification was effected. The principal series was first 
carefully projected on a scale of 4 miles to the inch, and the several 
rays emanating from stations of observation were next exactly drawn. 
The intersection of these rays, assisted by the characteristics forth¬ 
coming in the angle books, more or less distinctly defined the points 
sought for. This was treated as an approximate identification, 
whereby the bases required from the principal series and experimental 
triangles to be computed became known. The former were then 
obtained in the ordinary way, by means of the contained angle and 
logfeet of the including sides, for which computation the following 
well known formula was found useful, 
C 
tan | (A — B) = tan (45 — Q) Cot — 
2 
b 
wherein tan Q = — 
