THE 



CHALK AND FLINT FORMATION: 



ITS ORIGIN, &c. 



The question of the origin of the Chalk and Flint 

 formation cannot be considered as satisfactorily 

 determined by any of the hypotheses which have 

 been generally applied to the subject hitherto. One 

 or two of these may be briefly stated. 



It is a commonly-received theory that the chalk 

 has been the product of the accumulated shells of 

 minute infusorial animalculse at the bottom of the 

 sea ; and that the flints have been in some way 

 deposited from hot silicated springs, also at the 

 bottom of the sea, on their coming in contact with 

 reduced degrees of temperature. The manufacture 

 of the chalk by those microscopic animalculse is 

 supposed to be going on at present at the bottom of 

 the Atlantic. 



In regard to the forms assumed by the flint there 

 has been much difference of theory and conjecture. 

 Dr. Bowerbank, 1 on examination of thin slices of 

 flint under the microscope, thought he had ground 



1 Proceedings of the Geological Society, vol. iii., pp. 278 and 

 431 : Trans. Geol. Soc, Series 2, vol. vi., pp. 181, 188. pi. 18. 



B 



