THE TOPOGRAPHICAL SURVEY OF INDIA. 271 



twenty years ending in 1866. Combining these results, 

 we have an area of 524,000 square miles, or upward of 

 four times that of Great Britain and Ireland. For all 

 this enormous area the surveyors have the records in a 

 methodical and systematic form, fit for incorporation in 

 the atlas of India. Nor does this estimate include the 

 older revenue surveys of the northwestern provinces, 

 which, for want of proper supervision in former years, 

 were never regularly reduced. The records' of these 

 surveys were destroyed in the mutiny chiefly in Haz- 

 aumbaugh and the southwestern frontier agency. The 

 whole of these districts remain to be gone over in a 

 style very superior to that of the last survey. 



The extent of the country which has been charted 

 may lead to the impression that the survey is little more 

 than a hasty reconnoissance. This, however, is very far 

 indeed from being the case. The preliminary triangu- 

 lation, which is the basis of the topographical survey, is 

 conducted with extreme care. In the present Eeport, 

 for instance, we find that the discrepancies between the 

 common sides of the triangles in other words, the 

 discrepancies between the results obtained by different 

 observers are in some cases less than one-tenth of an 

 inch per mile ; in others they are from one inch to a 

 foot per mile ; and in the survey of the Cossyah and 

 Garrow Hills, where observations had to be taken to 

 large objects such as trees, rocks, etc., with no defined 

 points for guidance, the results differ by as much as 



