NATURAL THEOLOGY. 25 



and perhaps our limitted information will not enable 

 us to decide between them. The second suppo- 

 sition is, that the earth, being a mixed mass some- 

 what fluid, took, as it might do, its present form, 

 by the joint action of the mutual gravitation of its 

 parts and its rotatory motion. This, as we have 

 said, is a point in the history of the earth, which 

 our observations are not sufficient to determine. 

 For a very small depth below the surface, (but ex- 

 tremely small — less, perhaps, than an eight thou- 

 sandth part, compared with the depth of the 

 centre,) we find vestiges of ancient fluidity. But 

 this fluidity must have gone down many hundred 

 times further than we can penetrate, to enable the 

 earth to take its present oblate form ; and whether 

 any traces of this kind exist to that depth we are 

 ignorant. Calculations were made a few years 

 ago of the mean density of the earth, by compar- 

 ing the force of its attraction with the force of at- 

 traction of a rock of granite, the bulk of which 

 could be ascertained : and the upshot of the calcu- 

 lation was, that the earth upon an average, through 

 its whole sphere, has twice the density of granite, 

 or above five times that of water. Therefore it 

 cannot be a hollow shell, as some have formerly 

 supposed ; nor can its internal parts be occupied 

 by central fire or by water. The solid parts must 

 greatly exceed the fluid parts : and the probability 

 is, that it is a solid mass throughout, composed of 

 substances more ponderous the deeper we go. 

 Nevertheless, we may conceive the present face 

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