42 The Trigonometrical Survey of India. [No. 1, 
is 7SS6" = about the T ^y tli part of a circle described around our 
planet. And if tlie principal and mountain -operations of the North 
East longitudinal series be taken together, they will be found to 
cover somewhat more than the -yy— portion of the entire earth’s 
surface ; or, taking the land at half the expanse of water, about 1061 
such series would cover every portion of the former. 
80. Accuracy discussed .—And with regard to the accuracy of the 
mountain results, it is evident that the same estimate cannot equally 
apply to a peak with a sharp conical apex, and to a mountain whose 
summit represents a saddle back or an even bluff. Prominent amongst 
the accurately determined points are XIII. Mont Everest or XY. and 
XLII. or Dhoulagiri, both in respect to geographical position and 
height above sea level, but though such points are far more numerous 
than those which exhibit comparatively large differences between the 
several values composing their mean results, yet it is suggested 
that the synopsis of latitudes and longitudes and the paper of 
heights should be consulted before adopting a point, if necessary for 
rigorous purposes. 
81. The same estimated .—It is estimated, that on an average, the 
points on the Himalay a mountains are correct in latitude to y of a 
second and in longitude to about \ that quantity. The heights are 
probably true to 10 feet, but this last estimate must be qualified by 
the consideration that they are all too low from the deflection due to 
mountain attraction. 
82. Why mountain attraction teas not determined.—Ira the ori¬ 
ginal design of these operations, it was intended that the deflections 
in azimuth and in the meridian due to the attraction of the Himalaya 
mountains should be estimated along the principal series by suit¬ 
able celestial observations, but this intention was relinquished owing 
to the considerable delay it entailed. 
84. Area and cost .—The area covered by these principal and 
secondary operations amounts to about 61,815 square miles. But 
the piecemeal nature of work, the long intervals which frequently 
occur, and the unavoidable employment of the North East longitu¬ 
dinal series partly on other duties, make it a difficult and unsatisfactory 
process to attempt finding the cost of these operations. As an 
approximation, however, it may be stated that this cost does not 
exceed Rupees 2 per square mile. 
