253] VIBRATIONS OF A GLOBULE. 463 



Hence for a drop of water, putting T l 74, p = 1, we find, for the 

 frequency, 



0-/27T = 3'87a~* seconds, 



if a be the radius in centimetres. The radius of the sphere 

 which would vibrate seconds is a = 2 '47 cm. or a little less than an 

 inch. 



The case of a spherical bubble of air, surrounded by liquid, 

 is obtained by putting p=0 in (10), viz. we have 



* = (n + l)(-l)(n + 2)A ............ (12). 



For the same density of the liquid, the frequency of any given 

 mode is greater than in the case represented by (11), on account 

 of the diminished inertia ; cf. Art. 90 (6), (7). 



