IS POPULAR LECTURES AND ADDRESSES. 



subside, and the piece of matter will come to rest 

 in a spherical figure, slightly warmed as the result 

 of the work done by the forces of mutual attrac- 

 tion by which it was set in motion from the initial 

 shape. The work done by these forces during 

 the change of the body from any one shape to 

 any other, is in simple proportion to the diminution 

 of the whole surface area ; and the configuration 

 of equilibrium, when there is no disturbance from 

 gravity, or from any other solid or liquid body, 

 is that figure a sphere in which the surface 

 area is the smallest possible that can enclose the 

 given bulk of matter. 



I have calculated the period of vibration of 

 a sphere of water l (a dew-drop !) and find it to 

 be i/4.# 3/2 , where a is the radius measured in 

 centimetres ; thus 



For a radius of 1/4 cm. the period is 1/32 second 



I , 1/4 



2-54,, ,, i 



4 2 



,, 16 ,, ,, 16 



36 ,, 36 



1407 ,. 13,200 



1 See a paper by Lord Rayleigh in Proc. Roy. Soc. No. 196, 

 May 5, 1879. 



