]S62.] The Trigonometrical Survey of India. 33 



The North East Longitudinal Series was originally intended by 

 Col. now Sir George Everest, C. B. to have been carried along the 

 mountains on the British frontier. But this design was abandoned 

 in consequence of the refusal of the Nepalese Government to allow 

 the operations to enter their territories. Consequently, after crossing 

 the hills of Kumaon and Gurhwal, the triangles were brought down 

 into the Terai near Bareilly, from which point they lie almost con- 

 tinuously in the marshy and deadly tracts which fringe the Himalaya 

 mountains. Here Lt. Reginald Walker, a very able and promising 

 young officer, fell a victim to jungle fever. Being alone and without 

 medical assistance, he strove to reach Darjeeling, but was found dead 

 in his dhooly, on its arrival at that station. Of the native sub- 

 ordinates, a large percentage, one year no less than a fourth, died of 

 jungle fever. Sickness was frequent and severe. On more than 

 one occasion a whole party had to be literally carried into the nearest 

 station for medical assistance. The completion of the major, and 

 more difficult portion of the triangulation is due to the ability, 

 courage and perseverance displayed by Mr. George Logan, who died 

 three years afterwards, from disease first contracted in the Terai 

 during these operations. 



Owing to the proximity of the triangulation to the mountain 

 ranges, the whole of the chief peaks were seen from the principal 

 trigonometrical stations, and fixed by measurements with the first 

 class instruments employed for the mutual observations between the 

 stations themselves. These are called the " Principal Observations," 

 for on them, the accuracy and value of the series, as a whole, depend. 

 They are therefore taken with the largest and most powerful 

 theodolites, which are expressly constructed for the Indian Survey, 

 and furnished with micrometer microscopes, instead of verniers, for 

 reading the graduations. 



The employment of such instruments in secondary operations has 

 the advantage of enabling the observer to attain as great accuracy 

 by a few observations as by many with second class instruments, 

 thus time is saved and reliable measurements of the higher moun- 

 tains can be taken during the short intervals when their usually 

 cloud-capped summits are unfurled to view. 



The following extracts are chiefly relative to the computations for 

 determining the heights and positions of the principal mountains. 



