302 



THE WONDERS OF GEOLOGY. Lect. IV. 



of flint nodules, and the original substance of the fossil 

 is generally silicified, and the most delicate internal 

 structure preserved. In other instances the inclosed or- 

 ganisms have undergone no change, but appear as if 

 immersed and preserved in a semi-transparent medium ; 

 such is the state in which foraminiferous shells, corals, &c. 

 often occur. An exquisite example of this kind was 

 discovered by the Marquess of Northampton, in a chalk 

 flint from Brighton ; in polished slices of this specimen, 

 numerous branches of delicate corals ( Pustulopora, Mete- 

 pora, Idmonea, &c.*) and foraminifera, appear as perfect 

 and unaltered as if imbedded in glass. 



But there are innumerable flint nodules which exhibit 

 no traces of spongeous structure ; and veins, dikes, and 

 sheets of tabular flint, that may be regarded as pure, and 

 free from organic remains, excepting such as must inevitably 

 have become entangled and imbedded in a stream of mineral 

 matter flowing over a sea-bottom. Wood which has been 

 perforated by lithodomi, and silicified, is not scarce ; and 

 confervas and fuci are sometimes found floating, as it were, 

 in the liquid silex. Bones of reptiles and fishes are often 

 impacted in a mass of flint ; but in only one instance have 

 I observed that the silex has permeated the osseous 

 structure. 



7. Animalcules in flint. — For the most part, the 

 minute shells of the chalk and flint are filled with amorphous 

 mineral matter ; but in many examples, as I have ascer- 

 tained by direct experiment, f the soft parts or body of the 

 animalcule remain in the shell ; sometimes completely silici- 

 fied, but in others in the state of dried animal membrane, 

 like the ink-bag of the cuttle-fish in lias, the soft parts of 



* Medals of Creation, vol. i. p. 284. 



f See my observations u On the Fossil Remains of the soft parts of 

 Foraminifera, discovered in the chalk and flint of the S. E. of 

 England." Philosophical Transact ions, 1S4G, part iv. 



