THE ROTATION-PERIOD OF A HETEROGENEOUS SPHEROID. 



67 



concerned. This expression was found in 1898 by Mr. H. C. Wolfif, then 

 a graduate student at the University of Wisconsin. 



Investigations concerning the properties of the spheroid have usually 

 hypothecated an ellipsoid so nearly spherical that small error would be 

 introduced by neglecting the square of the ellipticity in comparison with 

 its first power. Such has been done in the present instance. For that 

 reason it is hardly possible to extend the computations to spheroids of 

 greater ellipticity than those given in the table. As a matter of fact, the 

 writer believes that he has extended the computations as far backward as 

 is practicable without straining the approximate formulas beyond their 

 limit of significance. 



The Rotation-'period of a Heterogeneous Spheroid. 



