456 The Surveys of India. [Oct., 



and its operations extend into such parts of the country as are 

 under British administration and yield a fair revenue. It is a defi- 

 nition and survey of village boundaries and estates, and may also be 

 termed a large scale topographical survey, as it affords accurate 

 topography of every district falling within the scope of its opera- 

 tions. The system followed is that of traversing with the theo- 

 dolite and steel chains, known as (rale's method of land-surveying, 

 modified to secure greater accuracy and efficient checks on both the 

 boundary and interior detail measurements. Large areas are first 

 traversed with the better class of small theodolites having from 12 

 to 8 inch horizontal circles, starting from an initial station, where 

 the azimuth is observed, to obtain the true bearings of stations in 

 advance, the distances between stations being measured with steel 

 chains twice over and repeated in rough ground, or wherever any 

 doubts arise. These traversed areas, called main circuits, being in 

 the first instance traversed and proved, afford a complete check on 

 the minor or block circuits into which they are subdivided; and 

 these minor circuits, being in their turn traversed and proved true 

 on the basis of the main circuit containing them, reduce the errors 

 in the village boundary work to a minimum. The trifling angular 

 and linear discrepancies which may occur in the village traverse 

 circuits are adjusted inter se. 



The interior or detail survey, which is filled in by plane-table 

 or compass and chain, rests on these small village polygons, plots 

 of which are furnished to the native plane-tablers. The stations of 

 the main circuits are permanently marked, and the masonry plat- 

 forms which mark the tri-junctions of villages are, whenever prac- 

 ticable, made theodolite stations. The boundaries of villages are 

 measured by offsets taken to all boundary pillars from the lines 

 enclosing the village polygons, these linear and offset measurements 

 being carefully recorded in the village boundary field-book. 



Along the Kevenue Survey lines of levels, all masonry platforms 

 marking the junction of three villages which fall on or near the line 

 are invariably adopted as permanent bench-marks. These being 

 all. marked prominently on the maps of the Revenue Survey, the 

 entry of the data will be readily and easily made, showing the 

 height of each bench-mark above the mean sea-level, as determined 

 by starting from and closing all the lines of Revenue Survey levels 

 on the Great Trigonometrical stations, or the bench-marks of the 



frincipal series of levels of the Great Trigonometrical Survey of 

 ndia. 



In connection with the Eevenue Survey, levelling operations 

 were carried on, during 1868-69, in Oudh and Rohilcund, and they 

 have subsequently been extended to the central provinces, Bha- 

 mulpoor and Bengal. The object of these is to run series of levels 

 across districts not yet contoured, and to combine the results of the 



