Siliceous Genus. 



I found loo parts of it to contain 25 of 

 mild calcareous Earth, and no iron. There 

 probably are two forts of ftone known by 

 this name, as Mr. Wallerius affirms that which 

 he defcribes, neither to give fire with fteel, 

 nor effervefce with acids. 



SPECIES XXIV. 



Siliceous Earth mixed ivitb mild Calcareous 

 Earth and Iron. 



Ragg-ftonc. 



Its colour is grey; its texture obfcurely la- 

 minar, but the laminae confift of a congeries 

 of grains of a quartzy appearance, coarfe 

 and rough; its fpecific gravity is 2,729; it 

 effervefces with acids, and gives fire with 

 fteel. I found it to contain a portion of cal- 

 careous Earth, and a fmall proportion of iron. 

 It is ufed as a whetftone. 



SPECIES XXV. 



Arenaceous Quartz confolidated by a fmalkr 

 proportion of Calcareous Earthy or Argill, 

 andftill a fmaller of Iron. 



Siliceous Grit y Sandjlone, Free/lone, Cos Are- 

 narius, Grais. 



Under this fpecies I comprehend only 

 fuch as ftrike fire with fteel, and when 



pounded, 



