1864.] Report of the Great Trigonometrical Survey. 401 



for the eventual calculations are being carefully elaborated by Lieute- 

 nant Herschel, to whom I am indebted for numerous very valuable 

 suggestions, and for co-operation as cordial as it has been unintermit- 

 tent. 



While the practical operations of this department may be confidently 

 pronounced to be of a superior order to similar operations in any 

 other part of the globe, it must, on the other hand, be admitted, that 

 the theoretical applications, for the reduction of the triangulation, 

 have not kept pace with recent improvements in geodetical science, 

 which have been introduced into some European Surveys. The method 

 which has hitherto been employed for reducing the observed angles, 

 so as to satisfy all the equations of condition of each figure, though 

 a great improvement on any previous method, has had, in its turn, to 

 give way to the subsequently discovered method of minimum squares. 

 The algebraical solution of the equations necessary to satisfy the 

 condition that the sum of the squares of the errors shall be a minimum, 

 is by no means difficult, but hitherto there has been no practical 

 adaptation of it in this Survey, chiefly owing to the pressure of other 

 and more urgent business, on those alone capable of dealing with the 

 subject. Much progress has, however, been recently made in this direc- 

 tion, and I am indebted to Lieutenant Herschel for devising methods 

 of calculation, which will enable the reduction of our figures to be 

 effected, according to the new and rigorous system, by native com- 

 puters possessing little more than a knowledge of arithmetic, with 

 even greater facility than the less refined methods of reduction, which 

 have hitherto been employed. 



The drawing office has been chiefly employed in compiling maps 

 of the dominions subject to the Maharajah of Kashmir, from the 

 plane table sheets sent in by Captain Montgomerie. A new Chart of 

 the Triangulation of this Survey, up to date, has also been prepared, 

 and a Chart to illustrate the volume of Tables of Heights recently pub- 

 lished; both these Charts were lithographed in the office of the 

 Surveyor General, Calcutta. Nine original preliminary Charts of the 

 triangulation, in various parts of India, have been prepared, in dupli- 

 cate, for the use of the Surveyor General's Office, and the Geographer 

 to the Eight Hon. the Secretary of State for India. The Photographic 

 apparatus is also being usefully employed in copying and reducing 

 maps, and in furnishing preliminary copies for current use, until the 



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