189 
LETTER XIX. 
FOSSIL TREES, IMBEDDED IN PEAT, HAVE UNDERGONE THE BITU- 
MINOUS fermentation THE CHANGES WHICH MOW-BURNT 
HAY UNDERGOES, SOMEWHAT SIMILAR TO THAT PRODUCED BY 
THE BITUMINOUS FERMENTATION. 
T HE fossil trees which are so frequently found imbedded in peat, 
may also be considered as vegetable fossils ; and as they appear to 
have undergone exactly the same kind, and the same degree, of 
mineralization with peat, their consideration along with that sub- 
stance seems to be proper. 
These trees, as appears by the accounts already given, are almost 
always found to have preserved their original form and structure so 
exactly, as frequently to render it easy to discover what species of 
trees they are, even in this their mineralized state. When first found, 
these trees are generally of a dark brown colour, manifesting, as has 
been already mentioned, the exact form of the original tree ; but so 
soft, as to be capable of being deeply cut into by the stroke of a 
spade ; ' and also of so spongy a texture, as to allow a very con- 
siderable quantity of water to be squeezed from them, even by a 
moderate degree of pressure. So tenacious are they of the water 
they have thus imbibed, as still to retain a very large portion of it, 
even where great pains have been taken to procure its expulsion. 
But when, after long exposure to the air, this water has been 
evaporated, the substance of these fossil trees assumes different de 
grees of solidity, dependent on the state in which the wood existe 
at the time of its exposure to the bituminous fermentation, and on 
