450 The Surveys of India. [Oct., 



The first base line measured by Colonel Lanibton was on the 

 table-land of Mysore, near to Bangalore. The chain used by him 

 was one of blistered steel, constructed by Eamsden, and precisely 

 similar in every respect to the one used by General Boy in mea- 

 suring his base of verification on Eumney Marsh. It consisted of 

 forty links of 2\ feet each, measuring in the whole 100 feet, at a 

 temperature of 62°, and fitted with two brass register-heads, with a 

 scale of 6 inches to each. This chain, it appears, had originally 

 been sent with Lord Macartney's embassy as a present to the 

 Emperor of China, and having been refused by him, it was made 

 over by his Lordship to the astronomer, Dr. Dinwiddie, from whom 

 it was purchased. The measurement of this base line was com- 

 menced on the 14th October, 1800, and completed on the 10th 

 December following. Its total length was 7*4321 miles. 



Whilst these operations were being carried on, an order was on 

 its way to England for a supply of instruments of the best manu- 

 facture that could be obtained. Amongst these was a new chain 

 which Colonel Lambton never allowed to be taken to the field, but 

 it was reserved as a test, whereby that actually used was constantly 

 verified. The other instruments received from England were a 

 36-inch theodolite, by Gary; an 18-inch repeating theodolite by 

 the same maker ; a 5-feet zenith sector, by Eamsden ; a standard 

 brass scale, by Gary; and several small theodolites, by different 

 makers, for minor purposes. These instruments were the finest 

 that the state of art at the commencement of the present century 

 could produce. 



On the 10th April, 1802, the real commencement of the Great 

 Trigonometrical Survey of India was made, although at that time 

 the extent to which those operations would be ultimately carried 

 was not even contemplated. Upon the resumption of operations 

 no notice appears to have been taken of the Bangalore base line. 

 "Work was commenced by the measurement of a fresh base line of 

 40006 - 4 feet, on a plane near Saint Thomas' Mount, Madras, at no 

 great distance from the shore, and nearly on the level of the sea. 

 Eroin this a series of triangles was earned, about 85 miles eastward, 

 north as far as the parallel of 13° 19' 49" N., and south to Cudda- 

 lore, in latitude 11° 44' 53", embracing an extent of about 3700 

 square miles. Before describing further the progress of the survey, 

 we must pause for a moment in order to give some account of the 

 care taken in measuring the base line. The chain was in all re- 

 spects similar to the one used at Bangalore. It was laid in coffers 

 or long boxes, supported on stout pickets driven into the ground, 

 and their heads dressed even by means of a telescope. At one end 

 of the chain was a draw-post, to the head of which the near end of 

 the chain being fastened, it could be moved a little backwards or 

 forwards by means of a finger screw. Near the handle of the chain, 



