Yl'ii PREFACE. 



which modern Authors rank with minerals Bovey- 

 coal, woodstone, and wood-opal, for instance (h). 

 At the same time, it will exclude common coal, 

 amber, and other bitumens, that no longer exhibit 

 the structure of the animal or vegetal matter, from 

 which they originate. 



The Graptolithi of Linnaeus and others (Petrifi- 

 cataficta) containing Dendritts, Landskip-marUes, 

 &c. are not, on any principle, to be admitted among 

 extraneous fossils. 



8. It is the cn^ganic form alone on which the 

 arrangement of reliquia must be founded. 



(h) This only when their structure is primarily considered 

 their substance, if it prove to be distinct from other known species 

 of mineral matter, must still be enumerated with minerals. 



Werner considers the matter of woodstone as a subspecies of 

 horneslone or chert that of bituminous wood or Bovey coal, 

 as a species of brown coal and that of wood-opal, as a sub- 

 species of opal. In each instance, however, the matter is cha- 

 racterized as differing from the primary species only in its vegetal 

 texture. Consequently, according to the principle above advanced, 

 it does not constitute a mineral species distinct from every other ; 

 but only a substance already determined, forming the material 

 of an extraneous fossil. 



