1870.] 



On the Indian Pendulum-observations. 



103 



At Alleppy the pendulum makes 2*41 vibrations more than at Mallapatti. 

 „ Mangalore „ 2*62 „ Bangalore. 



Bangalore. 



„ Madras „ 2*42 



„ Cocanada „ 2*78 



„ Calcutta ,, 3' 19 



„ Minicoy „ 3*90 



Kocundal. 



Ehmadpur. 



Punnse. 



(17.) I may observe that the coast stations were selected at places as 

 far removed as possible from mountain-ranges, in order that the results 

 might not be affected by the local variations of gravity under mountains. 

 For this reason additional stations could not be obtained on the west 

 coast, because to the north of Mangalore there is a range of mountains 

 running parallel to the coast at a very short distance. 



(18.) Having completed these observations, Captain Basevi returned to 

 the head quarters at Dehra Doon last April, taking a set of observations at 

 Kaliana en route, in order to ascertain whether the times of vibration of 

 the pendulums had sensibly altered, through accident or wear of the knife- 

 edges, in the period of four years which had -elapsed since 1866, during 

 which the apparatus had been transported (chiefly by land, but partly by 

 sea) over a distance of several thousand miles, and the pendulum had been 

 swung at twenty-two stations. The result indicates a slight alteration in 

 the pendulums, probably by wear of the knife-edges, to an extent equiva- 

 lent to one-third of a vibration in twenty-four hours. 



(19.) It now remains for Captain Basevi to investigate the true vacuum 

 and temperature corrections, by experiments under artificial temperatures. 

 He is at present making the requisite preliminary arrangements for the 

 purpose, and will commence the experiments as soon as possible. They 

 should be completed by the time that the snows of the approaching winter 

 are sufficiently melted to permit of the passes on the great southern ranges 

 of the Himalayas being crossed. Captain Basevi will then proceed to take 

 observations in the inner Himalayas, on three extensive tablelands which are 

 of great height, and are sufficiently removed from the neighbouring ranges to 

 obviate the necessity for minute calculations of the masses of these ranges, 

 calculations for which the requisite data are not forthcoming. The three 

 tablelands are "the plains of Deosai," lat. 35° 5', long. 75° 30', height 

 13,400 feet ; the plains north of the Changchenmo range, lat. 35° 15', 

 long. 79° 20', height 16,000 feet; and "the plains of Hanle," lat. 32° 

 50', long. 79°, height 14,200 feet. Captain Basevi also proposes to take 

 observations in the plains of the Punjab to the south of the Himalayas. 

 Finally, he will descend the Indus, and take observations on the coast at 

 Karachi, thus obtaining an additional coast station, which will be comple- 

 mentary to an inland station on Colonel Everest's Arc of the Meridian. 



(20.) It does not appear necessary that any more observations than these 

 should be taken in India. But in the proceedings of the Council of the 

 Royal Society in which the original programme of observations was dis- 



