if 



\ 



( 





niar, 

 Witi 



tbeii 



rilia 



led 



ha? 



)' 



edif. 



?6riei 



and, 

 rablj 

 jene- 

 ;anc( 



initE 



tll£ 



con- 

 beaf 



HUTTONIAN THEORY. 



25 



that careful and accurate examination of foflils, 

 in which he probably never was excelled by 

 any raineralogiil. It wHll be fufficient here to 

 point out a few of the moft remarkable exam- 

 ples. 



19. Foffil-wood, penetrated by filiceous mat- 

 ter, is a fubftance well known to mineralogifts ; 

 it is found in great abundance in various iitua- 

 tions, and frequently in the heart of great bodies 

 of rock. On examination, the filiceous matter is 

 often obferved to have penetrated the wood very 

 unequally, fo that the vegetable flrudture re- 

 mains in fome places entire; and in other places is 

 loft in a homogeneous mafs of agate or jafper. 

 Where this happens, it may be remarked, that 

 the line which feparates thefe two parts is quite 



fharp 



d diftind 



gether different from 



what muft have taken place, had the flinty mat- 

 ter been introduced into the body of the wood, 

 by any fluid in whicji it was diffolved. as it 



ould th 



h 



formly, yet 



pervaded the whole, if 



th 



a 



gular grad 



thofe fpecimens of foffil-wood th 



are 



penetrated by agat 



1. In 



partly 



d partly not penetrated 



at all, the fame fharpnefs of termination 



ay 



be remarked, and 



an 



ppearance highly ch 



deriftic of the fluidity produced by fufi 



20. The 



d 



d 



f fl 



that are 



found 



in chalk, quite infulated and feparate 



from 



I 



