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ening, even in some instances amounting to liquefaction. The last 

 change which it undergoes is produced, during that softened state, 

 by the addition of the saline im tallic solution, of which we have just 

 been speaking. From this long continuance, in a softened state, 

 and from the pressure of the superincumbent matters, we may rea- 

 dily account for this species of mineralized wood being found, 

 almost always, in a compressed state, and for its having undergone 

 this degree of compression, without having suffered any degree of 

 fracture. 



I do not, indeed, wonder at the scepticism which you say our 

 friend Wilton displays on this occasion ; since several very learned 

 men have been induced, by a consideration of this circumstance, 

 its oval compressed form, differing so much from the round shape 

 of common wood, to believe it to be entirely of subterraneous ori- 

 gin ; and that this compressed form was the grand characteristic of 

 wood of subterranean growth. 



But in many specimens of this kind of wood, such as those at 

 Plate VI. Fig. 1, and Fig. 7' so few of the ligneous fibres are dis- 

 coverable, that a section of them displays an almost uninterrupted 

 metallic surface. To explain this circumstance, it is only necessary 

 to consider that, in this case, there must have been a loss of the 

 ligneous fibre, which may be easily supposed to have taken place, 

 not only by the mechanical action of the water, whilst passing 

 through it ; but also at the time of the formation of the pyrites, 

 when some of the carbonaceous particles undergoing a degree of 

 oxygenation, and assuming a gaseous form, are employed in the for- 

 mation of carbonic acid ; whilst other portions, uniting with hydro- 

 gen, might contribute to the formation of carburetted hydrogen. 



I find myself, I acknowledge, much more disposed to concur with 

 him in his opinion, that the frequent discovery of a metallic sub- 

 stance, in a vegetable form, might have furnished the poet witii the 



