ON A PIECE OF CHALK 63 



those ancient pyramid-builders were terrestrial and air- 

 breathing creatures like ourselves, is it not better based than 

 the conviction that the chalk-makers lived in the sea. 



But as our belief in the building of the Pyramids by men 

 is not only grounded on the internal evidence afforded by 5 

 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 

 Globigerina that the chalk is an ancient sea-bottom, is forti- 

 fied by innumerable independent lines of evidence ; and our 10 

 belief in the truth of the conclusion 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 15 

 of the sea. 



The great mass of the chalk is composed, as we have seen, 

 of the skeletons of Globigerina, and other simple organisms, 

 embedded in granular matter. Here and there, however, 

 this hardened mud of the ancient sea reveals the remains of 20 

 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 25 

 anywhere but in the sea. Such are the corals ; those coral- 

 lines which are called Polyzoa; those creatures which fabri- 

 cate the lamp shells, and are called Brachiopoda ; the pearly 

 Nautilus, and all animals allied to it ; and all the forms of 

 sea-urchins and starfishes. 30 



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 



