56 THE UNIVERSE. 



hardest of our stones with one of the softest of animals, 

 because the one seems in some cases to be only a transfor- 

 mation of the other. 



Certain sponges, in lieu of having a soft and horny frame- 

 work, are composed of little hollows or fibres of flint; and 

 accordingly, so far from showing the flexibility of those we 

 ordinarily use, they are excessively fragile, and the least 

 pressure breaks them like glass. 



When this peculiarity is taken into account, the prox- 

 imity of the sponge to the flint appears less extraordinary, 

 for the detritus of the former would be adequate to produce 

 the other by its condensation. Indeed, some geologists 

 think that the flints of the chalk proceeded, if not entirely, 

 at least in great part, from the Sponges and Infusoria which 

 inhabited the cretaceous seas. The flints of some countries 

 even contain the debris of sponges ; remains of sponges are 

 also found in jaspers and agates. 1 



Thus a connection is established between one of the most 

 fragile organisms in creation and one of the hardest rocks, 

 the sponge and the flint. 



1 It is to Mr. Bowerbank that we are indebted for having shown that the flints 

 of different localities contain the remains of sponges. He also demonstrated that 

 the moss-agates of Germany and Sicily owe the peculiarity from which they are 

 named to the presence of sponges. Trans. Geol. Soc. v. 4. 



