112 MICROSCOPICAL OBJECTS FOUND 



Ehrenberg is done away with, so far as it is based 

 upon the alleged absence of flint from Infusorial 

 strata, and their presence where such Infusoria 

 are wanting. At the same time, this does not 

 prove that siliceous organisms may not have 

 been separated from the calcareous elements of 

 a rock, and subsequently brought together again 

 in a new form, constituting flint. If anything 

 of this kind has taken place, it could only have 

 been by the introduction of some agent capable 

 of dissolving the siliceous base of these structures, 

 and any such agent would of course also act upon 

 the siliceous sand grains, which occur more or 

 less abundantly in every calcareous stratum ; 

 consequently, if the Flint has really been derived 

 from the stratum itself, since sand grains are so 

 much more abundantly diffused than Infusoria, or 

 sponge spicula, even in the substance of the 

 Flamborough sponges, it is more likely that the 

 inorganic elements have been the usual source 

 rather than the organic, though of course both 

 would combine to produce the result. 



It is, however, more probable, that the Silica 

 has been derived from largely saturated hot 

 springs, as advocated by Dr. Mantell in his 

 "Notes on the Chalk and Flint of the south 



