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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 metallic 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 origin ; 
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 with the 
