IN THE MUD OF THE LEVANT. 105 



fossils ; still more easily can we conceive of water 

 containing carbonic acid slowly destroying the 

 smaller organizations of a Foraminiferous lime- 

 stone without producing any very great effect on 

 the larger structures. The solvent would act 

 upon the surfaces of the large and small fossils 

 with equal rapidity ; but what would obliterate 

 a Foraminifer, the two or three hundredth part 

 of an inch in diameter, would produce but little 

 change on the surface of a thick shell. 



There iire still many difficulties to be encoun- 

 tered in the settlement of this great question. 

 There is no doubt but that some strata, even of 

 recent date, which contain multitudes of Forami- 

 nifera and other small organisms, both entire 

 and in fragments, also contain large quantities of 

 amorphous calcareous matter which cannot be 

 directly traced to any such origin. The chalk 

 from the Missouri has been already alluded to as 

 of this character. It is not impossible that the 

 0])aque portions of the Missouri chalk may in 

 reality be the exuviae of the lower animals ; and 

 that the latter may have been the instruments of 

 an extensive conversion of lime from an organized 

 to an amorphous form. In the above instance it 

 is obvious that no external agents, acting gene- 



