€hessin — On the True Potential of the Force of Gravity. 5 



{d)s c ^= Kj- cos e 



3i\r 1 



-f -gT [1— 3sm2\-|-4sin2\sine + ^(— Il + 23sm2\)sin2e], 



(9)5 2e = — -g3- ~-gg- +-g^sin2x, 



.n «^ 2il^ 12i\r 36iV^ . ^ 



(9)6 2/= -gg- + -g-^ _ ^gg- sm 2\, 



we shall have 



(10)i "^ = a+2d^ + H, 



9U 

 (10). ^=2e,7. 



(10)3 |^=c+2/r+6|, 



and, therefore, 



(11) U=a^ + b^K + c^ + cZP + ev-" ^- jV, 



It may be well to note that the coefficients d^ e, f satisfy 

 the condition 



(12) cZ + e+/=0 



in accordance with Laplace's equation A, C7^= 0. 



6. A particle moving on the surface of the earth is subject 

 not only to the attraction by the terrestrial mass, but also to 

 the attractions by the sun and the moon. This latter influ- 

 ence is exercised in part directly, in part indirectly through 

 the medium of the tides, the liquid mass, which covers the 



