50 i HI. DIST. CHAR. Mode. 



Bituniiiiizatioa, or the process by which vegeta- 

 ble matter is converted into bitumen,, sometimes 

 takes place under circumstances,, which appear to 

 prevent its completion.^- The structure of the origi- 

 nal is then preserved ; as in wood and other vege- 

 table bodies found in peat, Bovey-cQal, &c. 



c. 4. IMPREGNATION (Imbutio). Under this pro- 

 cess the conservation is penetrated with mineral par- 

 ticles, which are mechanically f united with those 

 of the organic body., that still retain their original 

 structure. 



Obs. Impregnation may take place in all organic 

 matter pervious to water, the undoubted agent by 



the matter, and that of the oxide of carbon, from the ligneous. 

 After this, either the separation of the bituminous matter from the 

 carbonic takes place (wholly or in part} leaving the latter in the 

 state we find it in Bovey coal, and other varieties of bituminated 

 and carbonized fossil wood ; or a new combination is effected be- 

 tween the carbonic matter and the bitumen thus formed: by 

 which means, the texture of the original body is completely de- 

 stroyed, and every vestige of organization, for the most part, lost 

 in the production of the more solid and compact bitumens, as 

 Asphaltum, Jet, &c. and the numerous varieties of pit-coal, into 

 which the pure or simple bitumens naturally graduate. (For a 

 number of most excellent observations on the formation of bitu- 

 minous substances, the reader is referred to Mr. Hatchett's well 

 known papers in the Philos. Trans. 1804, and the Linman, v.IV.) 

 } Not chemically in which impregnated conservata differ 

 from such of the converted, as have had their change brought 

 about by a chemical union, between the organized particles and 

 principles derived from the surrounding miuerals. 



