190 AN ACCOUNT OF THE 
good observer at each place, with one or two assistants, good instruments, 
and great alacrity, and the mean of alternately repeated flashes; and to 
such extent as they may be visible, this method is above all astronomical 
operations, for determing differences of longitude, the most certain. But 
to return to the subject immediately under consideration. Having received 
my instructions, I proceeded from the army, on the immediate frontier of 
Nepal to the upper part of the Doab in the Sehdranptr district, in which, 
orin the Déhra Din, or valley, I intended to begin my operations, by 
measuring a base of four or five miles in length, if the ground should prove 
favorable. On examining the plain lying at the southern foot of the hills, 
between the Ganges and Jumna, I found there were several placés where 
I might measure a line of three or four miles, but that on account of 
the mango groves, with which the country is studded, it would be very — 
difficult, if not impossible, to extend the sides of the triangles, which would 
increase in length considerably, before I could prolong them to the feet of 
those low hills, which divide the plams from the Din. On the summits 
of the last mentioned hills, I intended to establish stations proper for ob- 
taining others, on those loftier mountains, which bound the Din to the 
north, and command views of the Himdlaya peaks, as well as of the 
plains. When the distances between some of these points, and Sehdran- 
ptr, as well as their reciprocal distances from each other, should be esta- 
‘blished, I intended to use those lines as bases, whereon to determine the 
positions of the snowy peaks, as has since been done. The search of the 
ground having proved unsuccessful in the plains, I proceeded, for the pur- 
pose of making a similar examination, to the Din, to search for more favor- 
able ground. The Din, though a valley, has an uneven surface, sloping 
