which possesses the characteristic Properties of Tannin. 137 
vegetables are totally or partially buried under the waves or 
under the earth, they are not merely by such means con- 
verted even into the most imperfect sort of coal.* Some 
process therefore independent of these circumstances must 
have taken place, in order that the vegetable substances, such 
as ligneous matter, resin, oil, & c. should become coal and 
bitumen. 
In a former Paper I have endeavoured to shew, that these 
changes are progressive, and having noticed the perfect state 
of the submerged wood at Sutton and other places, I next 
described the qualities of the different kinds of Bovey coal, 
which exhibit a series of gradual changes from bodies which 
retain the vegetable structure and texture, although imper- 
fectly carbonized, to others in which almost the complete 
characters of the common mineral or pit-coal are absolutely 
established. 
From the alder leaves in the schistus from Iceland, I ob- 
tained extractive vegetable matter, and although this was not 
* In my Paper, “ On the Change of some of the proximate Principles of Vegetables 
“ into Bitumen ” I have quoted the remarks of Bergman, Von Troil, and others, 
on the compressed state of the trunks of the trees which have been converted into 
surturbrand, Bovey coal, and similar substances. The same observation has been 
also made by Dr. Correa de Serra respecting the timber of the submarine forest 
at Sutton ; and this is the more remarkable, as the submerged vegetables at Sutton 
do not exhibit any appearance of carbonization. 
Dr. Correa says, “ In general the trunks, branches, and roots of the decayed 
“ trees, were considerably flattened ; which is a phenomenon observed in the surtur- 
“ brand or fossil wood of Iceland, and which Scheuchzer remarked also in the 
fossil wood found in the neighbourhood of the lake of Thun, in Switzerland.’"’ 
Phil. Trans. 1799, p. 147, 
MDCCCVI. T 
