42 The Trigonometrical Survey of India. [No. 1, 



is 7886" = about the T ^ ill part of a circle described around our 

 planet. And if tbe principal and mountain operations of the North 

 East longitudinal series be taken together, they will be found to 

 cover somewhat more than the ^^2 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 XV. 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 Himalaya mountains are correct in latitude to \ 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 was not determined. — In the ori- 

 ginal design of these operations, it was intended that the deflections 

 in azimuth and in the meridian clue 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. 



