72 
[ASSEMBLT 
It is a curious fact, that in this water the sulphate of lime is in the 
largest proportion, while no trace of it can be discovered in the tufa. 
If this be true of all these springs, the sulphate of lime must be con- 
verted into a carbonate at th*e moment of its deposition, or soon after 
that deposition has taken place. 
It has been conjectured that the conversion of vegetable into mineral 
matter is intimately connected with the phenomena of slow putrefac- 
tion, and that these must be studied whenever we attempt to reason on 
the conversion of fossil bodies into stone. 
In many of the specimens found in Chittenango, the petrified leaves, 
apparently of the beech, are much thicker than those which have not 
undergone this change. And from the prominence of the midrib and 
nerves, I am induced to think that the change commenced with the de- 
cay of the fleshy part of the leaf, and was completed by that of the 
more solid or woody portions. 
If the ccmposition of this petrifying water has been correctly deter- 
mined; it contains sulphate and carbonate of lime, each of them proba- 
bly held in solution by a slight excess of acid. Now vegetable matter 
consists essentially of carbon, hydrogen and oxygen, the two latter be- 
ing gaseous, while the carbon is solid and gives form to the different 
parts of the plant. May notj then, the decomposition of the vegetable 
be promoted by this sulphuric acid, which combines with the hydrogen 
and oxygen, or water of the vegetable, and leaves the carbon? And 
may it not be the carbon remaining after the action of the acid, which 
causes the change of the sulphate into the carbonate of lime, and which 
at the same time also abstracts a portion of the oxygen in the carbonic 
acid, which holds the carbonate of lime in solution, and thus causes the 
deposition of the latter substance? 
If these questions are answered affirmatively, I think we can account 
for the fact, so apparent in examining these petrifactions, that oftentimes 
the most perishable portions of the plants are preserved ; for the carbon 
is the solid matter of the vegetable, and is that constituent to which it 
owes its form. But this, according to the suggestion here made, leaves 
its state of carbon only to be converted into carbonate of lime, and 
this last being also solid, the vegetable form is preserved. 
I have, perhaps, occupied more space with this subject than may be 
thought proper. But the process is one of great interest, and the evi- 
* Lyell's address to the Geological Society of London, 1837. 
