cu 



^^ 



200 



SPHEROIDAL FORM OF THE EARTH. 



[Ch. XXXIL 



which alone could retain their several parts in a state of 

 equilibrium ? 



Let us^ however^ concede that the statical figure may be 

 a modification of some other pre-existing form^ and suppose 

 the globe to have been at first a perfect and quiescent 

 sphere^ covered with a uniform ocean— what would happen 

 when it was made to turn round on its axis with its present 

 velocity? This problem has been considered by Playfair 

 in his Illustrations ; and he has decided, that if the surface 

 of the earthy as laid down in Hutton's theory, has been 

 repeatedly changed by the transportation of the detritus of 

 the land to the bottom of the sea^ the figure of the planet 

 must in that case, whatever it may have been originally, 

 be brought at length to coincide with the spheroid of equi- 

 librium."^ Sir John Herschel also, in reference to the same 

 hypothesis^ observes, ^ A centrifugal force would in that case 

 be generated, whose general tendency would be to urge the 

 water at every point of the surface to recede from the axis. 

 A rotation might indeed be conceived so swift as to flirt the 

 whole ocean from the surface, like water from a mop. Bub 

 this would require a far greater velocity than Avhat we now 

 speak of. In the case supposed, the iveight of the water 

 would still keep it on the earth ; and the tendency to recede 

 from the axis cotdd only be satisfied therefore by the water 

 leaving the poles, and flowing towards the equator j there 

 heaping itself up in a ridge, and being retained in opposition 

 to its weight or natural tendency towards the centre by the 

 pressure thus caused. This, however, could not take place 

 without laying dry the polar regions, so that protuberant 

 land would appear at the poles, and a zone of ocean be 

 disposed around the equator. This would be the first or 

 immediate effect. Let us now see what would afterwards 

 happen if things were allowed to take their natural course. 



' The sea is constantly beating on the land, grinding it 

 down, and scattering its worn-off particles and fragments, 

 in the state of sand and pebbles, over its bed. Geological 

 facts afford abundant proof that the existing continents have 



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* Illust, of Hutt. T]ieory,-§ 435—443. 



