MEASURE OF A DECREE ON THE COROMANDEL COAST, 4| 



sidere(J at the same distance from the centre of the earth, 

 before it was reduced to the level of the sea, and the per-r 

 pendicular height of the south extremity, vvhich I have conr 

 sidered as nearly the general height, has been taken for that 

 purpose. That perpendicular height was obtained by com- 

 paring the south with the north extremity, and the height of 

 the latter was deterrnined by observations made at the race- 

 gtand and on i}ie sea-beach, where allowance has been made 

 for the terrestrial refraction. T|ie following i^ tjie manner 

 in which it has been determined : 



On the top of the race-stand, the u^der part of the flag Determinafioj^ 

 on the beach was gbservecj to be depressed 9' 30' ; and at j^jj^y^jjigfe^ 

 the beach, the top of th^ race-stand was elevated 7' 15". 

 When the instrument wa? oiji the platform of the race-stand, 

 the axis of the telesjpope was on & level yvith the top of the 

 railing, which was observed frpm the beach. But at the 

 beach the axis of the telescope was four feet below the part 

 of the flag which had been observed. 



The horizontal distance from the station on the stand to 

 that on the beach js — 19208 feet. Then as 192O8 : 4 : : 

 Rad ; tan. 43", which must therefore be added to the ob- 

 served depression pf the flag. Hence 9' 30' + 43" =10' 13' 

 is the depression of the axfis qf the telescope on the beach, 

 observed from the race-stand. 



Now the station on the beach is nearly at right angles 

 to the meridian, therefore, by allowing 60957 fathoms to 

 the degree, 192.08 feet will give an arc of 3' 9" very 

 nearly, which is the contained arc. And the difierence be- 

 tween the depression and elevation being 2' 58", we have 

 "^^ r: 5"'5 for thje terrestrial refraction. Hence, 



since the observed elevation pf the st^nd, plus half the con- 

 tained arc, would give the angle subtended by the perpen- 

 dicular height of the ptand above the telescope at the 



beach, were there no refraction, we shall have 7 15" + -—- 



— 5"'5 rr 8' 44" for the true angle subtended by the p^- 

 pendjcular height, which being taken as tangent to the ho- 

 rizontal distance and radius, we have R ; tan. 8' 44" : : 

 19208 : 48797 feet the height required. But the axis of 

 |hje telescope pn the beach was determined, by levelling; 



down 



