Tuomson.—Colonial Standard Survey. 97 
The system of great triangulation cast over India is not that of “ net 
work” as cast over the British Islands, but what is technically termed 
“ gridiron " or ** chain series." In this respect it imitates the systems of 
Russia and France, Thus though all the immense extent of territory has 
been embraced, yet not more than one-fifth of the whole can be said to be 
triangulated. The Madras portion is an exception to the above rule only, 
which is ** net work." The ‘chain series ’’ pursue meridians at intervals of 1 
to 2 degrees of longitude, and follow parallels at intervals of 1 to 5 degrees of 
latitude. But there are several great areas unaffected even by these ; such 
as the region east of Scinde, extending 420 miles east and west, and about 
845 miles north and south, the region of Orissa, of equal extent—other 
regions in various parts uncovered being smaller than these. 
In the series of the largest triangles theodolites 86 inches in diameter 
are used in India, each requiring 27 men for their transport. 
At the commencement of Lambton's operations in India it is interesting 
to note that objections to great triangulation were raised by the eminent 
geographer Rennell, he proposing an astronomieal instead of a geodetie 
basis; but Lambton, amongst other arguments in his reply, showed that in 
the breadth of the Indian Peninsula an astronomical error of 40 miles had 
occurred—in the position of the city of Arcot 10 miles and Hydrabad 82 
miles, all in longitude; hence in those days longitude was the difficulty. 
Had the wonderful properties of the electric telegraph as applied to this 
very subject then been known, it is possible that the controversy would have 
ended in the support of Rennell, not in overturning great triangulation in 
its elucidating the problems of meridian arc survey, but in curtailing its 
extension beyond that process. 
I have not been able to obtain any authentic return of the cost of great 
triangulation in Britain, and as there have been ample records of the same 
system in India, I refer to the following :— 
Sq. miles £ ok d. 
Everest’s great arc series .. .. | 56,997 | cost d 833 | 111 7 per square mile 
uber longitudinal.. s ja 15,198 » 13,742 | 018 8 i 
Budoa do is n .. | 12,468 s 14,259 A. 5 D 2$ 
faligheur do ip e <é [46,087 s 41,897 014 9 5 
Amua do zl ENS . 10495. 119 9 si 
Karara meridional longitude. 5 5,819 ,. ii 9 6 2 s 
Guriwani do ja 6,298 2 ; 89011 0 I7 0 ES 
Gora do ca s. | 4,416 » 4594] 114 8 js 
Chundwar do 8,565 » 6,450 17185 5 a 
Parimath north meridional longitude 4,765 s Oomi I 23 » 
Caleutta mendosa longitude 4,136 », 11,0900] 2 18 8 5 
Highest £2 18s. 8d. per mile, lowest 17s. The mean cost of great or 
primary triangulation may thus be taken at £1 11s. 9d, per square mile. 
M 
