1863. | Progress of the Trigonometrical Survey. 121 
late 5th Bengal European Cavalry, second Assistant, have made good 
progress, having in the two field seasons been carried from a point 
near Mitunkote, on the Indus line of levels, to the Dehra Dhoon 
Base Line, vid Bahawulpoor, Ferozpoor, Loodiana, Umballa and 
Saharunpoor, and thence on to the Seronge Base line in Central In- 
dia, via Meerut, Allygurh and Gwalior, over a distance of 999 miles. 
In the course of these operations, stone bench marks were fixed at 
distances of 12 to 15 miles, and the most substantial milestones met 
with by the road side were also determined, for future reference by 
Canal or other Engineers engaged in levelling operations. A satis- 
factory connexion has been made with the Ganges, and the eastern 
Jumna Canal levels, and with those of the Allahabad and Agra Rail- 
way, which are now capable of being reduced to the mean sea level 
as a common datum. 
20. The ComeutTineé Orrice in Calcutta, under the superinten- 
dence of Baboo Radanath, chief computer, was engaged in completing 
the triplicate manuscript volumes of the General reports of the Paris- 
nath, Hurilong and Chendwar Meridional Series, and in furnishing 
elements for the various Topographical and Revenue Survey Parties 
requiring them. In March last, Baboo Radanath retired on a pen- 
sion, after 80 years’ service, during which he had repeatedly earned 
the approbation of the successive Surveyors General under whom he 
had served. On his resignation it was deemed advisable to remove 
the computing office from Calcutta to the Head quarters of the Tri- 
gonometrical Survey at Dehra Dhoon, to bring it into more direct 
amounts. On this curious and perplexing subject, Captain Branfill reports as 
follows : 
“ T think we can all subscribe to the following facts—The state of the weather 
and the season of the year havea very considerable effect on our results, as 
shown by the difference between observers. We have found that the apparent 
law of our differences is least developed some time in the middle of the cold sea- 
son. Inarun of bad weather (@. e. bad for the work) the apparent law of our 
difference is for the most part marked when the atmosphere is clearest, and when 
we have supposed our observations to be freest from error ; and conversely in a 
run of good weather, when the air is hazy from smoke or dust, or greatly agitated 
by wind, and, in short, when we have found most difficulty in reading the staves, 
our results have most coincided with each other. Our differences do not appear 
to vary with the distances of the staves, On the contrary the differences are per- 
haps even more marked as the day grows older, and the distances of the staves 
from the instrument are reduced. The general direction in azimuth of the line 
of our work has some connection with the cumulative differences, and we have 
noticed that the tendency to differ is more marked when proceeding towards a 
certain point of the compass, than when proceeding from that point towards its 
opposite.” 
