390 



I have lately obtained, yields a beautiful instance of this sub-im- 

 pregnation with copper. The ligneous form and texture, with even 

 the knots, are perfect. The colour in some parts differs but very 

 little from that of decayed wood, whilst the central part demon- 

 strates the strongest marks of its having undergone the bituminous 

 fermentation ; and the surface, tinged, more or less, of a greenish 

 hue, is marked by a few spots of malachite : the whole demonstrat- 

 ing, that an impregnation, with a solution of carbonate of copper, 

 had taken place, and had arrested the progress of the bituininizat- 

 ing process. 



The combination of the other metals with fossil wood is not very 

 frequent. Some authors, and particularly Volkman, have spoken 

 of wood impregnated with silver. That this may have been the 

 case is by no means improbable ; at the same time, it is not to be 

 positively concluded, that the specimens, of which they speak, were 

 impregnated with this metal ; since it is not said that they had been 

 submitted to any chemical test ; and the brilliance of some pyrites 

 is such, that, although they do not contain the least particle of 

 silver, they frequently exhibit the splendour, and the whiteness of 

 that metal. 



The respectable author of Outlines of an Attempt to establish a 

 Knowledge of extraneous Fossils on scientific Principles, and of Petri- 

 Jlcata Derbiensia t informs us in the former of these works, p. 150, 

 that he has seen specimens of fossil wood, thoroughly impregnated 

 with lead, or rather galena. A specimen is now before me, from Lord 

 Bute's Museum, which is evidently thus impregnated. 



Yours, &c. 



