ON THE PHYSICAL STRUCTURE OF THE EARTH. 219 



Pi—P= 'j//.[j/*, and 2" .58, if we take the Moon's inass = ^. 



On calculating P with the Moon's mass=:y^, Snn's mass 354936, y is 

 2-25395. If we take for 1 its value in 1852, or 23^ 37' 32", and make 



w=359o-9931, -=-0027303, ^=.ver=fTg, 

 n 



the following calculations can be made. 



log;][G0x00J 



3-732393J; 

 '4-1998437' 



1 n 2-40754S9 , ^o,, «oo 



log Pi =1~7^22948='''S' ^3 -^^^^ 



or Pi =54" nearly, Pi~P=3"-G17. 



Consequently instead of admitting Mr. Hopkins's result of 7" for the 

 difference between the precession of a homogeneous spheroid with the 

 Earth's ellipticity and the precession actually observed, we may affirm 

 that this difference is probably not more than 4" or 5". 



With the best values for the numerical elements the difference is, 

 however, too well ascertained to be overlooked, and it leads to the con- 

 clusion that the Earth can not consist of an entirely solid mass composed 

 of equi-elliptic strata, and that it is therefore partly composed of a solid 

 shell bounded by surfaces such as I have elsewhere indicated, with an 

 interior mass of viscid liquid, such as is seen flowing from the volcanic 

 openings of the shell, arranged in strata conforming to the laws of 

 hydrostatics, or in other words, with strata of equal density decreasing 

 in ellipticity toward the Earth's center. 



