•360 Professor Airy on a Correction of the Pendulum. 



diameter, the allowance to be made must be 64 times as great, 

 or line : a quantity perhaps sensible, or which would at least 



alter the figures in the last decimal places of Biot's estimations. 



Had the diameter of the balls been twice as great, in the 

 last experiment, the error would have been of a magnitude 

 greater than could occur in any comparison of standards. 



It appears then that by a happy chance the error of esti- 

 mation arising from the neglect of this consideration has not yet 

 been sensible, though it has closely approached the limit of 

 perceptible error. As a guide in future experiments, I shall 

 give a short statement of errors corresponding to given magni- 



R 2 

 tudes of the spheres, supposing — - ~ . 



1 i5 



The length of the seconds' pendulum being estimated in the 



Tf 3 



usual way, the quantity to be added in inches is 4,27 x Cj\ . 



T> inch. 



If J = ,01 this is 0,000004, 



. - ,02 0,000034, 



,03 0,000115, 



R 



I 



R 



I 



R 



I 



R 



I 



R 



y = ,1 0,00427. 



J = ,04 0,000273, 



J = ,05 0,000534, 



G. B. AIRY. 



Observatory, July 2, 1829. 



