444 G. E. Darwin— Influence of Geological Changes 



I forbear, however, to discuss this subject more fully at 

 present, the Admiralty not having yet published the final 

 fit of the ''Challenger" temperature-sections. And I 

 niie myself to an expression of my earnest hope that 

 the ship to be sent next year to communicate with the Arctic 

 Expedition may have, as part of its work, the completion of' 

 that which the "Valorous" was disabled from performing — 

 namely, the obtaining a continuous temperature-section between 

 Iceland and G r I >avis Strait. 



Art. XLIX.— On the Influence of Geological Changes on the 

 Earth's Axis of Rotation ;* by George H. Darwin, M.A., 

 Fellow of Trinity College, Cambridge. Eeceived by the 

 Koyal Society October 13, 1876. f 



The subject of the fixity or mobility of the earth's axis of 

 rotation in that body, and the possibility of variations in the 

 obliquity of the ecliptic, has of late been attracting much 

 attention ; but the author believes that it has not hitherto been 

 treated at much length. The paper, of which the following is 

 an abstract, is an attempt to investigate the results of the sup- 

 position that the earth is slowly changing its shape, with 

 especial reference to the effects on "the obliquity of th 

 and on the geographical position of the earth's axis of figure. 



1. This part of the paper is devoted to the consideration of 

 the precession and nuts >id of revolution which 



is slowly and uniformly changing its shape. The change is 

 supposed to proceed from causes internal to the earth, and only 

 to continue so long as the total changes in the principal 

 moments of inertia C and A remain small compared to their 

 difference, C— A. 



The problem is treated by means of M. Liouville's extension 

 of Euler's equations of motion of a rigid body about a pointf 

 By an approximate method these equations may be treated as 

 linear, and the solution divided into two parts. 



Let 6 be the obliquity of the ecliptic ; n cosec the preces- 

 sion of the equinoxes ; — n the angular velocity of rotation of 



iii, 1858, p. 1 ; Routh's Rigid Dynam, p. 1 



