which possesses the characteristic Properties of Tannin. 139 
This opinion may in some degree be refuted even from the 
specimens afforded by the Bovey coal-pits, where, as I have 
observed, a regular gradation may be seen from wood which 
is biit very imperfectly carbonized, to the substance called 
stoiie coal, which in every respect appears to be most nearly 
if not absolutely similar to the common pit-coals.* 
It may however be objected, that such a transition is pecu- 
liar to this and similar places, and that the pit-coal found in 
other situations, where nothing resembling the Bovey coal 
can be discovered, is in reality of a different nature. 
But this objection I think may be answered by the results 
of those experiments on pit-coal, Cannel coal, and asphaltum, 
which I have related in the third section of this Paper ; for 
when these were subjected to the action of nitric acid not 
too long continued, it was found, that the acid first dissolved 
the principal part of the carbonaceous matter, and if then the 
process was stopped, there remained a substance in a pro- 
portion Corresponding to that of the bitumen either in the 
pit-coal, or principally forming the Cannel Coal and asphal- 
turn, which although not absolutely in the state of resin, was 
how r ever in a state intermediate between it and the vegetable 
extractive matter. 
Moreover I have stated, that under similar circumstances, 
a substaiice possessing in a great measure the same properties, 
may be obtained from the known vegetable resins by the 
action of nitric acid. 
When therefore, these facts are added to that of the 
* Phil. Trans. 1804, p, 398. 
T 2 
