560 VISCOSITY. 



In the First Class we have 



p = const., 



d d 



and therefore xu + yv 4- zw = 0. 



In the Second Class we have 



[CHAP, xi 



(8); 



.(9). 



and 



(11), 



where f, ?;, f denote the component rotations of the fluid at the 

 point (x, y, z). The symbols ^ n , <f> n , p n stand for solid harmonics 

 of the degrees indicated. 



The component tractions on the surface of a sphere of radius r 

 are given by 



d 





y...(i2). 



In the solutions of the First Class we find without difficulty 



