M. Von Buch on the Silicification of Organic Bodies. 61 



where the mouth of the animal would have been situated. We 

 might believe it possible here to distinguish even the spreading 

 out of the cloak of the animal around this muscular mass. It 

 is very worthy of remark, that the shell is converted into a sili- 

 ceous hydrate, while the animal, on the contrary, is converted 

 into flint. ]?ut this latter still contains within it the organic 

 substance itself, which distils out of it as an animal oil. 



It is even this animal oil which makes the above substance 

 flint, as, without this admixture, it would be only a purer quartz. 

 And although it may appear strange, still the fact is certain, 

 that the most regular strata of flint between the chalk, even 

 when we can trace them for many miles, are still nothing else 

 than silicicated organic remains, consisting principally of coral?. 

 With some attention we easily discover this to be the fact ; and 

 in this case, likewise, we remark that it is not the calcareous co- 

 vering, but the animal corals themselves, which have been con- 

 verted into flint ; and that this has been the case abundantly, 

 and with such precision and exactness, that the inner structure 

 of the animal of the coral can be investigated and observed, not 

 unfrequently, far better in the silicicated than in the living 

 state. 



I have never remarked that flint formed warts and concen- 

 tric waves, like the siliceous hydrate ; perhaps it is even on this 

 account that flint is not a hydrate, and never assumes a gelati- 

 nous consistence. 



Testaceous animals which, when they increase in size, leave 

 the chamber which they had hitherto inhabited, and pass to a 

 new one, very seldom become silicicated ; because the deserted 

 chamber cannot strengthen itself, by depositing new lamella?. 

 Neither does there remain on the shell, nor in the inside of it, an 

 organic substance, which can become silicified. Therefore, the 

 examples of silicified Ammonites or Nautiluses are not common. 

 And when Belemnites are found in the state of calcedony, it is 

 not the alveolae which are silicified, but only the fibrous apex 

 in which a new layer had been deposited by means of every 

 growth of a new chamber in the cell. On this account, the si- 

 licified apex is almost always brown ; and by carefully dissol- 

 ving it in diluted acids, the organic matter between the fibres 

 and layers will frequently appear. 



