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sequent pursuit. He was severely wounded at the siege of Delhi, and 

 was actively engaged in several of the wars with frontier tribes. But 

 his real life-work was connected with the surveys of India, and it is 

 on his services as a scientific geodesist of a very high order that his 

 title to fame must rest. His military reconnaissance and survey of 

 the Trans-Indus Region, during which he mapped upwards of 8,700 

 square miles of previously unexplored country, almost single handed, 

 between 1849 and 1853, though most important in itself, was mainly 

 a preparation for his work connected with the Great Trigonometrical 

 Survey of India. 



Walker entered that department in 1853, and served in it for 

 thirty years. This long time of most arduous service is divided into 

 two distinct periods. For the first eight years he was under Sir 

 Andrew Waugh, while for the remaining twenty-two years he was 

 himself in charge, and latterly he undertook the control not only of 

 the trigonometrical, but of all the other surveys of India. While 

 under Sir Andrew Waugh, from 1853 to 1861, he was engaged on 

 the northern section of the Indus series of triangles, and also on the 

 measurement of the base near Attock, and afterwards on the Jogi 

 Tila meridional series. When Sir Andrew retired, in 1861, Major 

 Walker was marked out as his successor. He had already received 

 high praise for the character of his geodetic work, and his chief had 

 thus addressed him : — " The brilliant success which invariably attends 

 your undertakings is a proof of the high professional qualifications, 

 the foresight, and judgment which you bring to bear on the im- 

 portant geodetical work on which you are engaged." 



Walker assumed charge of the survey at a time when much re- 

 vision had become desirable owing to improvements in the instru- 

 ments, and also at a time when it was within the range of reasonable 

 hope that the great triangulation might be completed within the 

 period of his own term of office. He first completed the last three 

 meridional series in the north of India, and measured the Vizaga- 

 patam base, and then turned his attention to a revision of Colonel 

 Lambton's early triangulation s in the Madras Presidency, and to a 

 re- measurement of the Bangalore base. In 1873 he began to devote 

 much attention to the dispersion of unavoidable minute errors in the 

 triangulation, and it is an acknowledged fact that no trigonometrical 

 survey in Europe equals that of India in accuracy. A great work 

 was undertaken under Colonel Walker's auspices, with a view to pre- 

 serving a complete record of the various operations of the Great Trigo- 

 nometrical Survey, which is now contained in twenty volumes. The 

 first nine were edited by W alker himself, the first appearing in 

 1871, and he wrote the introductory history of the early operations 

 of the survey, the accounts of the standards of measure and of the 

 base lines, the descriptions of the methods of procedure and of the 



