On a Piece of Chalk 87 



ternal evidence, of the essential identity of the chalk 

 with modern deep-sea mud. Globigervue, coccoliths, and 

 coccospheres are found as the chief constituents of both, 

 and testify to the general similarity of the conditions 

 under which both have been formed.* 5 



The evidence furnished by the hewing, facing, and super- 

 position of the stones of the pyramids, that these structures 

 were built by men, has no greater weight than the evi- 

 dence that the chalk was built by Globigenna; ; and the 

 belief that those ancient pyramid-builders were terrestrial 10 

 and air-breathing creatures like themselves, is 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 15 

 by these structures, but gathers strength from multi- 

 tudinous collateral proofs, and is clinched by the total 

 absence of any reason for a contrary belief; so the 

 evidence drawn from the Globeriginte that the chalk is 

 an ancient sea-bottom, is fortified by innumerable inde- 20 

 pendent lines of evidence; and our 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 25 

 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 Globigerints, and other simple 



* I have recently traced out the development of the " cocco- 30 

 liths " from a diameter of ^ fa Q th of an inch up to their largest 

 size (which is about ^ fa flth), and no longer doubt that they 

 are produced by independent organisms, which, like the Globi- 

 gennte, live and die at the bottom of the sea. 



