536 The Rev. S. Haughton on Physical Geology. [Dec. 20, 



axis is the new axis of maximum inertia, and that this motion by which 

 the pole revolves uniformly on a circle of 138 miles diameter, completing 

 each revolution in 304*75 days, will continue for ever unless stopped by 

 friction. 



In one day the pole moves through 1*423 mile; but while the solid 

 globe (supposed rigid) revolves round each instantaneous axis in succes- 

 sion, it is not so with the ocean, which tends to revolve round yesterday's 

 axis until compelled to revolve round today's axis by the friction of the 

 ocean against its sea-bed. This friction may be thus taken account of. 



Second Approximation. 



In the accompanying figure, let 

 OC be the new axis of figure, 



OA ,, the fixed meridian from which the angle u is measured, 

 Oy „ yesterday's axis of rotation, 

 Ot „ today's axis of rotation, 



Oy' „ the projection of yesterday's axis on the equator of figure, 

 Of „ the projection of today's axis on the equator of figure, 

 ah „ the day's path of the pole, 

 Oy" „ drawn at right angles to Oy', 

 Ot" „ drawn at right angles to Of', 



u;=AOy', 

 du—y'Ot', 



dd = aOh = yOt= the daily angle described on the surface of the 

 cone. 



It is evident that Oy" is perpendicular to the meridian COy' (yester- 

 day's), and that Ot" is perpendicular to the meridian CO? (today's). 



