416 ON THE FORMATION OF THE CHALK STRATA, 



the delicate ramifications that are thus laid open to view? Cer- 

 tainly not with any degree of probability, by the deposition of 

 the calcareous matter, or the infiltration of the siliceous, as 

 suggested by Werner ; nor is the forcible introduction of sili- 

 ceous matter, as suggested by Dr Hutton, at all compatible 

 with such delicate structures. 



I am aware of the temerity of offering any thing like a new 

 doctrine on the formation of the materials I have been now 

 ti^ating of, and perfectly sensible of the desire which, in spite 

 of us, exists among us all, to find objections to any novelty of 

 the kind, rather than to contribute our mite to its support, or 

 to trouble ourselves about the investigation of the grounds on 

 which it is established. Still, however, I cannot help stating, that 

 after pondering upon this subject, and taking into account all that 

 I am acquainted with respecting the strata of chalk-rocks, it ap- 

 pears to me that they must have been deposited in a very quies- 

 cent state; that the calcareous and siliceous matter had, by 

 their respective attractions, separated, and that the latter was 

 deposited in thin and multiplied continuous seams, in the man- 

 ner conceived by Daubuisson ; that the fossils were promiscu- 

 ously intermingled throughout, when the specific gravity of each 

 was equal, so that they occur in all parts of the stratum ; that the 

 whole was, according to Dr Hutton, exposed under pressure to 

 a great degree of heat, which not only attenuated the substance 

 of the carbonate of lime, and rendered it capable of being for- 

 ced into the minutest cavities of the fossils ; but also, by fusing 

 the thin seams of siliceous matter, enabled that substance, by 

 new and more powerful attractions, to collect itself in the sphe- 

 rical and tuberose groups it now exhibits, enveloping the fos- 

 sils which were previously intermixed with it, and, from the 

 pressure it maintained, forcing its way into all the cavities 

 in the organic bodies, however minute, that happened to be 



among 



