Forces derivable from a Potential of the Second Degree. 45 



(39 + 23 1) - 3 ,* + 6, 3 ) - ^~ (6 + 13 // + 36 ,* + 25 ? 3 ) J 



(9 + 13 V +27, 2 



(24), 







(26). 



zz maybe obtained from ?/^, and zx from a-t/ by interchanging y with 

 z and 6 with c. 



The redaction in length along the axis of rotation is given by 



2a 2 b c 2 24 + 223 <? -f 282 7y 2 + 95 

 ~"^~ "6 



5 ??*"| 

 J* 



It is thus greater or less than in a sphere of radius a, according 

 as a? is less or greater than the arithmetic mean of the squares on 

 the principal semi-axes. The tendency to shorten in the axis of 

 rotation increases as the perpendicular diameters lengthen. 



For the increment in a perpendicular semi-axis b, we get 



lblb = 



7+5, 



, 



