123 



repairing the sewer there, and was given me by Thomas 

 Furley Forster, Esq., F. L. S. It was very loose in the outer 

 texture, and is quite solid within, losing the appearance of 

 Wood, having the hardness and fracture of Flint, with a 

 colour like that of Wood. It is stained black in some 

 parts, having the appearance of burnt Wood. In this 

 specimen we can scarcely determine whether it had been 

 scorched or blackened by artificial fire, (as is sometimes 

 done with Wood to give durability, and to prevent its 

 rotting,) or by a natural process, more gentle. The piece 

 figured below came from Derbyshire by favour of Mr. 

 Martin, and is nearly black all over, excepting the outside, 

 where it seems the bark may have covered it. This black- 

 ness gives it the appearance of having been charred by fire ; 

 but fire in the usual way must have affected the outside by 

 stains or smoke, &c. : this therefore is an extraordinary 

 appearance, and difficult to be accounted for with certainty. 

 It is however to be seen, in some specimens which I possess, 

 that the charring process may be effected by the natural pro- 

 gress or decomposition, which is continually seen to take 

 place as far as our limits extend, and all over the surface, of 

 the globe. The Silex in this specimen, by attempting to 

 crystallize, has rendered it somewhat granular, and has 

 in some measure destroyed the finer and more delicate parts 

 of the Wood. 



I do not at present hazard a conjecture about what kinds 

 of Woods these are. I have had many opinions from good 

 judges about them; but must wait for further experience 

 and more varieties. The remains of petrified woods, im- 

 pressions of plants, &c. in different states are very uni- 

 versal. In coal-countries, and sometimes in other places, 

 the Carbon and Bitumen often pass into Coal, or new com- 

 binations under the influence of their particular situations. 



