MERIDIAN ON THE COAST OP COROMANDEL. ISQ 



old one only as a measuring chain, by which means I 

 can always determine the correction for the wear. 



By referring to the annexed table, it will appear 

 that there are only four angles of depression, and two 

 of elevation, taken in the whole length of the base ; 

 the rest are all horizontal measurements, and many 

 of them consist of a great number of feet before it 

 became necessary either to sink or elevate the cof- 

 fers; when that was done, great care was taken to 

 mark the termination of the preceding measurement ; 

 and for that purpose a small tripod was used in the 

 shape of a T, with three iron feet to run into the 

 ground, the straight side of which T was placed in 

 the line. Another small t was made with its top 

 also parallel to the line, and fixed upon the large 

 one so as to slide to the right or left, and upon that 

 again was a long piece of brass made to slide out at 

 right-angles to the top of the T ; in the middle of 

 this brass a mark was made, which was brought to 

 a plumb line let fall from tl\e arrow, and the height 

 from the brass to the arrow was noted down ; when 

 the succeeding chain was laid, which was to com- 

 mence the new level or hypothenuse, the arrow was 

 then brought, so that a plumb line freely suspended, 

 would coincide with the mark on the brass slider. 

 The height of that chain above the brass was like- 

 wise taken, by comparing those two heights the ele- 

 vation or depression of the new commencement was 

 determined, and those differences noted in the se- 

 venth and eigth columns of the table. The difl'erences 

 of the two aggregates contained in those coluinns, 

 when applied to the ascents and descents, will there* 

 fore shew how much one extremi-ty of the base is 

 above the other. The height of the c!iain at the 

 commencement and termination of the whole was of 

 course taken from the ground. 



All the other particulars respecting this measure- 

 nient are nearly the .same as that in the iMjsore coun* 



