CREATION OF ANIMALS. 21 



sins Kircher in his Mundus subterraneus, but 

 merely to inquire whether there are any pro- 

 bable grounds for thinking that some creatures 

 may be placed by their Creator at such a depth 

 within the earth's crust, as to be beyond all 

 human ken. 



When Laplace says, " It is certain that the 

 densities of its (the eartJis) strata increase from 

 the surface to the centre, "it seems to follow that, 

 in his opinion, there is no central cavity in our 

 globe ; but as his object was chiefly to assert the 

 increasing density of the strata as they approach 

 the centre, perhaps his words are not to be 

 taken strictly, especially as in another place he 

 speaks of it merely as probable that the strata 

 are more dense as they are nearer to the centre. 

 Sir I. F. W. Herschel makes a similar, but less 

 exclusive observation, using the terms, " towards 

 the centre," which is not inconsistent with a 

 cavity. 



But after all this is matter of conjecture built 

 upon the attraction of the earth, and cannot be 

 ascertained by actual examination ; as far as that 

 has been carried, it does not appear that in the 

 present state of our globe the strata always lie 

 exactly in the order of their densities ; in the 

 original earth probably they did. But now we 

 tread upon the ruins of a world that has been 

 almost destroyed and reformed. " The struc- 

 ture of the globe," observes an eminent geogra- 



