IV] INCRUSTATIONS. 69 



water highly charged with carbonate of lime readily deposits 

 calcium carbonate on objects placed in the path of the stream. 

 The travertine deposited in this manner forms an incrusta- 

 tion on plant fragments, and if the vegetable substance is 

 subsequently removed by the action of water or decay, a mould 

 of the embedded fragment is left in the calcareous matrix. An 

 instructive example of this form of preservation was described 

 in 1868' by Sharpe from an old gravel pit near Northampton. 

 He found in a section eight feet high (fig. 10), a mass of incrusted 

 plants of Chara (a) resting on and overlain by a calcareous paste 

 (c) and (d) made up of the decomposed material of the overlying 

 rock, and this again resting on sand. The place where the section 

 occurred was originally the site of a pool in which Stoneworts 



Fia, 10. Section of an old pool filled up with a mass of Chara. (Prom the Geol. 

 Mag. vol. v. 1868, p. 563.) 



grew in abundance. Large blocks of these incrusted Charas may 

 be seen in the fossil-plant gallery of the British Museum. 



In the Natural History Museum in the Jardin des Plantes, 

 Paris, one of the table-cases contains what appear to be small 

 models of flowers in green wax. These are in reality casts 

 in wax of the moulds or cavities left in a mass of calcareous 

 travertine, on the decay and disappearance of the encrusted 

 flowers and other plant fragments^. This porous calcareous 



1 Sharps, S. (68) p. 563. 



" There are still more perfect casts from Suzanne in Prof. Munier-Chalmas' 

 Geological collection in the Sorbonne. The best examples have not yet been 

 figured. 



