436 
In 'the specimen depicted Plate IV. Fig. 5, a circumstance is ob- 
servable, which is, in this place, highly deserving of observation. 
Lhwydd and others remark, that sometimes, though rarely, the leaf 
will be found so well preserved, that even the colour may be dis- 
cerned : and in this specimen the marks of the leaves are evidently 
of a very dark olive green. But an accurate inspection with a lens 
demonstrates that the same circumstance has occurred here, which 
is. frequently met with in the bituminization of wood — ^the bitumi- 
nous matter retains the colour of the vegetable substance from 
which it derived its origin — that which appears to be the leaf being 
evidently a thin shining bituminous film. 
Yours, &c. 
LETTER XLVII. 
FOSSIL FLOWERS THEIR EXISTENCE DOUBTFUL FOSSIL SEEDS 
AND SEED VESSELS FOSSIL FRUITS. 
W HEN the extreme delicacy of structure is considered, which 
belongs to the flowers of plants, little expectation can be enter- 
tained of often finding these in a petrified state. The tender and 
almost succulent substance of the petals, stamina, and pistilla, 
will furnish very little reason for supposing, that they should resist 
a destructive resolution, sufficiently long to allow them to pass 
through those chemical changes, by which such duration would 
be given to their original forms, as would secure their passing 
unchanged, in their figure, from the vegetable to the mineral 
kingdom. 
