THE TOPOGRAPHICAL SURVEY OF INDIA. 273 



less than Jive inches ! As we have stated, the trigono- 

 metrical survey of India will bear comparison with the 

 best work of our surveyors in England. 



A revenue survey is prosecuted for the definition 

 of the boundaries of estates and properties. The op- 

 erations of such a survey are therefore carried on con- 

 formably to those boundaries. 



The topographical survey of a country is defined by 

 Sir A. Scott "Waugh to imply " the measurement and 

 delineation of the natural features of a country, and 

 the works of man thereon, with the object of producing 

 a complete and sufficiently accurate map. Being free 

 from the trammels of boundaries of properties, the 

 principal lines of operations must conform to the fea- 

 tures of the country, and objects to be surveyed." 



The only safe basis for the topographical survey of 

 a country is a system of accurate triangulation. And 

 where the extent of country to be surveyed is large, 

 there will always be a great risk of the accumulation 

 of error in the triangulation itself ; which must there- 

 fore be made to depend on the accurate results obtained 

 by the great trigonometrical operations. In order to 

 secure this result, fixed stations are established in the 

 vicinity of the great trigonometrical series. Where 

 this plan cannot be adopted, a net-work of large sym- 

 metrical triangles is thrown over the district to be sur- 

 veyed, or boundary series of triangles are carried along 

 the outline of the district or along convenient internal 



