890 Heport of the Great Trigonometrical Survey. [No. 4 



of Eastern Bengal ; in lieu of the present solid mass of earthwork it 

 will be necessary to bnild a masonry wall around the central pillar, to 

 support the observer's platform. 



The Eahoon Meridional Series, under the superintendence of Mr. 

 H. Keelan, First Assistant G. T. Survey, was brought to a ter- 

 mination during the last Field Season, by being extended southwards 

 until it joined the Great Longitudinal Series of Triangles, connect- 

 ing Calcutta and Karachi. The meridional distance triangulated is 

 sixty -nine miles, by thirteen principal triangles, arranged in polygons, 

 for mutual verification, and covering an area of 1,603 square miles. 



This Series has taken six years to accomplish. It was commenced 

 by Mr. Logan, late First Assistant G. T. Survey, but has been 

 chiefly executed by Mr. Keelan. It is double throughout, the triangles 

 being arranged in successive quadrilaterals and polygons of remarkable 

 symmetry. Its meridional length is 457 miles ; the principal and 

 secondary triangles cover an area of 23,620 square miles. The 

 computations and maps connected therewith will be completed by 

 the 1st October, when the party will be transferred to the districts 

 on the meridian of 84°, between Sumbulpoor and the East Coast. 

 The total cost of the operations, up to 1st October, will be about 

 Eupees 2,01,609, which gives a rate of Eupees 8-8-6, or about 17 

 shillings per square mile. 



The field operations of the Gurhagurh Series, on the meridian 

 of Umritsur, were brought to a termination at the end of season 

 1861-62, when it formed a junction with the series of triangles on the 

 same meridian which had been brought up by Captain Eivers as far 

 as Ajmere, from the Great Longitudinal Series. By the 1st October, 

 1862, the recess computations and charts were completed, and the 

 party was available for transfer elsewhere. This Series has taken five 

 years to complete ; the greater portion has been executed by Mr. 

 George Shelverton. Its meridional length is 557 miles; the area 

 covered by the principal and secondary triangles, 19,096 square miles ; 

 the cost, Eupees 1,08,212, which gives a rate of Eupees 5-10-8, or 

 about 11 shillings per square mile. 



The Sutlej Series follows the left bank of the Sutlej from its 

 junction with the Indus, near Mithunkote, to a side of the Gurhagurh 

 Series near Ferozepoor. It was commenced towards the close 01 

 Field Season 1860-6 L by Lieutenant Herschel ; and was completed 



