58 GREAT TRIGONOMETRICAL SURVEY OF INDIA. 



arid British Burma into Tenasserim, and closed on to a base-line of 

 verification in Mergui, near the southern extremity of the British 

 territory east of the Bay of Bengal. Thus the principal triangula- 

 tion of all India had been completed on the lines originally marked 

 out by Colonel Everest and sanctioned by the Honourable Court of 

 Directors of the East India Company, A brief retrospect of the 

 history of this great undertaking, epitomized from General "Walker's 

 excellent account thereof, may be here given. 



The Great Trigonometrical Survey of India originated in a 

 so-called " mathematical and geographical survey," which was 

 commenced in Southern India, in the year 1800, by Major Lambton 

 of H.M.'s 33rd Regiment of Foot, on the recommendation of the 

 Honourable Colonel Wellesley, afterwards Duke of Wellington. Its 

 object was, in Major Lambton's words, to " determine the exact 

 " positions of all the great objects that appeared best calculated 

 " to become permanent geographical marks, to be hereafter guides 

 " for facilitating a general survey of the peninsula;" and as at 

 that time the elements of the figure of the earth were not known 

 Avith sufficient approximation to enable the latitudes and longitudes 

 of the " great objects " to be computed with accuracy from the data 

 of the triangulation, Major Lambton pointed out that his intended 

 survey would, in the interests " of general science involve many 

 " more objects than that immediately appertain to geography," 

 and that portions of the triangulation would have to be executed 

 with the utmost possible precision, and be supplemented by astro- 

 nomical determination of position, with a view to the requirements 

 of geodesj . 



Between the year 1800 and 1825 the operations consisted of a 

 network of triangulation over Southern India, grounded on, and 

 verified by, several chain-measured base-lines, through the middle 

 of which a principal chain of triangles was carried in a meridional 

 direction, from Tape Comorin up to Sironj in Central India. This 

 chain formed the southern portion of what is now known as Lambton 

 and Everest's Great Arc. Its angles were measured with greater 

 care than those of the collateral network, and at certain of its 

 stations astronomical observations of the latitude were taken for 

 the determination of the included minor arcs of amplitude. Colonel 

 Lambton died in 1*23. and was succeeded by Colonel Everest, who 

 found no difficulty in obtaining carte blanche from the Government 



