. III. DIST. CHAR. Substance. 141 



a primary formation,, is the matrix, and some- 

 times the substance,, of petrifactions. 

 Aluminous Slate. Kirw. v. 2. p. 19. F. An. 

 particularly of Ammonitae. 



* * * Trappose Stones. 

 HornU.nde. 



Common. Jam. p. 357. has been observed 

 forming the nuclei to testal reliquia. v. 

 Kirw. G. Ess. p. 252. 

 Trap. 



Figurate, or Basalt. Kirw. p. 231. F. An.?? 

 Wacke. Jam. p. 376. F. Veg. ? ? according to 

 Sanssure, Abbe Fortis, Bruckenman, Jame- 

 son, Dr. Richardson,, &c &c. both animal and 

 vegetal remains have been detected in Basalt 

 and Wacke. But though it is admitted that 

 these stones sometimes (rarely indeed) form 

 the matrix, it is still a question,, if they ever 

 constitute the substance,, of extraneous fos- 

 sils. 



* * * * Aggregate Stones. 

 Argillaceous Sandstone. Kirw. p. 363. F. An. 



and Veg. mostly the latter. 

 Rubble stone. Kirw. p. 366. shells, v. Lesk. 

 Mus. Coll. G. n. 874. 



***** Mica. 



Glimmer. Kirw. p. 210. is frequently dispersed 

 through the sandstones and clays forming ve- 

 getal petrifactions, but never constitutes their 

 whole substance. 



