1864.] JReport of the Great Trigonometrical Survey. 



381 



Extract from Report of the Operations of the Great Trigonometrical 



Survey of India during the year 1862-63. — By Major J. T. 



Walkek, E. E. Superintendent Gr. T. Survey. 

 [Received 10th November, 1863.] 



In accordance with the sanction of Government, I proceeded, 

 in the autumn of 1862, with the officers and assistants marginally 

 detailed,* to Vizagapatam to measure a Base Line. Vizagapatam is 

 situated nearly on the same parallel of latitude as Bombay ; and is 

 the point where the Bombay Longitudinal Series, when extended 

 eastwards to the Madras Coast, will terminate. This series of tri- 

 angles will form, with the Great Arc Meridional, the Calcutta Longi- 

 tudinal, and the Coast Series, a vast quadrilateral figure, circumscribing 

 the Meridional Series of triangles which are required as a basis for 

 the interior topographical details. Base Lines had been measured 

 several years ago, by Colonel Everest, at Beder, Seronj, and Calcutta, 

 the S. W., N. W., and N. E. angles of this quadrilateral. One 

 more Base Line remained to be measured, which, for considerations of 

 symmetry, it was desirable to place in the vicinity of Vizagapatam. 



Captain Basevi, the officer in charge of the Coast Series, being 

 located at Vizagapatam, was directed to select the site. After several 

 trials, owing to the difficulty of carrying a straight line, several miles 

 in length, so as to avoid the numerous irrigation tanks with which 

 this district is studded, he eventually succeeded in finding a suitable 

 line, on the undulating plain between the Military stations of Vizaga- 

 patam and Vizianagram, at a distance of about fifteen miles to the 

 west of the port of Bimlipatam. The ground was chosen before the 

 commencement of the rainy season of 1862, when trenches were dug 

 to carry away the expected rain fall during the monsoon, and every 

 precaution was taken to keep the line dry. But when Captain Basevi 

 took the field early in October, he found that the rains had been so 

 heavy, that the surrounding tanks had been converted into lakes, and 

 the line lay submerged under a sheet of water, in some parts as much 

 as sixteen feet deep. By great exertions the water was drained off 

 into adjoining ravines. A portion of the line was ready for measuring 

 on my arrival in December, and the remainder had become fairly dried 

 by the time it was reached, in the course of measurement. 



* Messrs. Hennessy, Taylor, Campbell, Wood, Burt and Mitchell. 



