3862.] 
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 
che 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. 
