64 GREAT TRIGONOMETRICAL SURVEY OF INDIA. 



On hills and mounds the central pillar is raised two to four feet above 

 the ground level, and is surrounded with a platform of earth and 

 stones. Mark-stones engraved with a dot and surrounding circle to 

 define with precision the point to which the observations a.re 

 referred, are inserted on the surface and at the base of each pillar. 

 The stations are invariably placed under the protection of the local 

 officials; they are scattered over 33S British, districts and Native 

 states, in each of which some officer is required to submit annual 

 reports of the condition of the whole of the stations within its 

 circle; repairs are effected whenever necessary. If the present 

 system of protection and repairs is maintained by future generations 

 of officials, the duration of the stations should be coeval with that 

 of the hills and plains on which they stand, and the great work now 

 completed will be of lasting utility. 



A considerable amount of secondary triangulation has been 

 executed pari passu with the principal triangulation, partly by 

 observations from the principal stations to all the most, prominent 

 objects visible from them, as the snowy peaks of the Himalayan 

 range, and partly by the construction of chains of secondary triangles 

 resting on the primary chains, such as have been carried to a number 

 of important towns and cities within the limits of the Empire, and of 

 late years beyond these limits, to Kandahar and Khelat on the one 

 side, and to Bangkok on the other. Much secondary triangulation, 

 however, still remains to be executed. Until recently it was wanted 

 on the coast lines to furnish fixed points for the marine surveys, 

 and in localities in the interior at a distance from the nearest prin- 

 cipal chains, where data may be required for topographical surveys. 

 But it is chiefly wanted outside the limits of India proper, as for 

 the extension of the Eastern Frontier Series through the Malayan 

 peninsula down to Singapore, and to furnish a basis for the 

 geography of Upper Burma. For the latter purpose three chains 

 on the meridians of 94 ". 96 . and 98 respectively are desirable, the 

 two first of which would close on the chain of secondary triangula- 

 tion already completed it: the Assam valley, while the third might 

 be carried still further to the north. Bangkok, the capital of Siam, 

 having already been connected with the Indian triangulation by a 

 chain of triangles, which was recently executed with the support of 

 the Siamese Government. 



The requirements of geodesy necessitate astronomical observations 

 for the determination of the latitude and the azimuth, and electro 



