ON A PIECE OF CHALK 75 



Pyramids by men is not only grounded on the internal 

 evidence afforded by these structures, but gathers strength 

 from multitudinous collateral proofs, and is clinched by the 

 total absence of any reason for a contrary belief; so the 

 evidence drawn from the Globigerince that the chalk is an 

 ancient sea-bottom; is fortified by innumerable independent 

 lines of evidence; and our belief in the truth of the conclu- 

 sion to which all positive testimony tends, receives the like 

 negative justification from the fact that no other hypothesis 

 has a shadow of foundation. 



It may be worth while briefly to consider a few of these 

 collateral proofs that the chalk was deposited at the bottom 

 of the sea. The great mass of the chalk is composed, as we 

 have seen, of the skeletons of GlobigerincB, and other simple 

 organisms, imbedded in granular matter. Here and there, 

 however, this hardened mud of the ancient sea reveals the 

 remains of higher animals which have lived and died, and 

 left their hard parts in the mud, just as the oysters die and 

 leave their shells behind them, in the mud of the present seas. 



There are, at the present day, certain groups of animals 

 which are never found in fresh waters, being unable to 

 live anywhere but in the sea. Such are the corals; those 

 corallines which are called Polyzoa; those creatures which 

 fabricate the lamp-shells, and are called Brachiopoda; the 

 pearly Nautilus, and all animals allied to it; and all the 

 forms of sea-urchins and star-fishes. Not only are all 

 these creatures confined to salt water at the present day; 

 but, so far as our records of the past go, the conditions of 

 their existence have been the same: hence, their occurrence 

 in any deposit is as strong evidence as can be obtained, 

 that that deposit was formed in the sea. Now the remains 

 of animals of all kinds which have been enumerated, occur 

 in the chalk, in greater or less abundance; while not one oi 



