33 



MR. J. B. HANNAY ON SILICEOUS FOSSILIZATION. 



least disfigured. In fig. 2 we see a beautifully preserved 

 sample of Fenestella; and we know that a very slight 

 solvent action would have destroyed the structure of these 

 delicate organisms . From other internal evidence^ such as 

 little shells and diatomacese, it is clear that the calcareous 



portion of this limestone has not been at any time dissolved 

 to any extent ; and yet such an obdurate substance as silica 

 has been completely removed. Then^ as to the cause of its 

 removal. The solution was no doubt highly calcareous ; 

 but we know that highly calcareous water may run over 

 quartz crystals for a very long period without having the 

 slightest effect upon the faces. I think that fig. 3 will 



