CONFIGURATION OF THE EARTH. 49 



the abstract nature of any of these forces, to consider 

 what configuration their combined action would give 

 to a globe more or less resembling the earth, sup- 

 posing the action of each of these forces to be such as 

 described in volume L 



191. For the sake of illustrating the action of these 

 forces, let us suppose a globe in space : of which, let 

 the outer covering be air ; beneath that air an un- 

 broken expanse of water ; beneath that water a 

 hardening, but still more or less pliant, surface of 

 land; and beneath this land, or outer crust of the 

 globe, a fluid incandescent mass homogeneous with 

 the materials whose solidification has formed the 

 outer crust, or land. 



Under the sole action of its own force of gravita- 

 tion that globe would naturally tend to preserve its 

 form as a perfect sphere. 



If, however, in that globe there be induced a 

 motion of rotation round an axis passing through 

 its centre, then by that motion a centrifugal force 

 is created, acting from the axis towards those parts 

 of the surface which, being most remote from the 

 axis, rotate with the greatest velocity. On the 

 surface of the globe, this force would act from the 

 poles of the axis towards the equator. And, supposing 

 the land or outer crust of the globe to be sufficiently 

 pliant, then the liquid mass within it would bulge it 

 out all round the equator and draw it inwards at 

 each of the poles; thereby causing its equatorial to 



VOL. II. E 



