DOMAIN II. 



SILICEOUS. 



SILEX, SILICA, OR SILICEOUS EARTH. 



THIS earth derives its name from the 

 silex, or flint, in which it abounds. Some 

 also denominate it quartzose earth, be- 

 cause it is perhaps more abundant in the 

 stone called quartz, which, when trans- 

 parent and crystallised, is styled rock crys- 

 tal. It so frequently occurs in the form 



