VALUE OF GRAVITY AT THE SYDNEY OBSERVATORY. 



63 



The Sydney observations, details of which are given in a paper 

 communicated by the present writer to the Royal Society of 

 Victoria,* have a special interest, inasmuch as they allow the 

 value of gravity at Sydney to be determined by comparison with 

 three independent absolute determinations ; one of these — probably 

 the most reliable — was executed at Kew by the officers of the 

 Indian Survey;! another at Greenwich by Sabine ;| and the third 

 at Melbourne by Neumayer. The full details of the Melbourne 

 determination have not yet been published, but the result is known. 



In order to obtain from these observations the value of gravity 

 in Sydney we require to know the daily number of vibrations — 

 executed in vacuo and under a uniform temperature (62° F.), 

 and reduced to sea level — of the three invariable pendulums at 

 each of the four above mentioned stations : these are given in the 

 following table : 







TABLE I. 







Station 



Sydney. 



Greenwich.* 



Melbourne. 



Kew.* 



Observer 



Love. 



Hollis 



Baracchi. 



Constable. 



S (No. 4 

 1 \ No. 6 

 | (no. 11 



86095-95 

 8599597 

 86047-25 



86165-19 

 86065-09 

 86116-83 



86107-89 

 86008-05 

 86059-69 



86165-84 

 86066-37 

 86116-61 



* These values for Greenwich and Kew are quoted from the recalculation in Baracchi's 

 paper. (Loc. cit.) 



If we subtract the Sydney values from those given for the other 

 three stations we obtain the following table of differences : — 



TABLE II. 



Pendulum 



G— S. 



M.-S. 



K.— S. 



No. 4 



69-24 



11-94 



69-89 



No. 6 



691 2 



12-08 



70-40 



No. 11 



69-58 



12-43 



69.36 



This table sufficiently demonstrates the degree of consistency 

 of the observations. 



* Loc. cit. 



f Report of the Great Trigonometrical Survey of India, Vol. v., p. 267. 



X Phil. Trans., 1831, Art. xxv. 



