424 
Geology. 
aquatic animals ; and of these, chiefly shell fish, as shells 
are not so soon decomposed as mere animal substance. 
Coal and bituminous substances, will also occur in the 
latter fioetz or secondary formations only ; for with me 
there is no doubt of these being the produce of submerg- 
ed vegetables, subjected to the effects of heat modified by 
compression. The many specimens I have seen at 
Whitehaven and elsewhere in England, and some Ame- 
rican specimens that I possess myself, wherein there is an 
evident gradation and passage from wood to coal in the 
same piece, compels me to adopt this opinion. The pro- 
cess of nature in converting wood into coal, I do not pre- 
tend to have satisfied myself about. 
The latest deposits of what is considered as the secon- 
dary series ot formations, will comprehend basalt, wacke, 
greystone, amygdaloid, newer limestone, chalk and calk 
sinter, obsidian, pumice, pitch stone, ^ (I have found this 
among primitive rocks at the mills near Baltimore) coal, 
gypsum and rock salt, which two last usually keep com- 
pany in this series ; argillaceous iron ore, petrifactions, 
&c. 
The remains of land animals are nearly confined to the 
newest floetz and alluvial deposits. The remains of many 
land animals, have been found, particularly by Cuvier, of 
which the race does not now exist. So La Marck has 
found remains cff aquatic animals similarly circumstanc- 
ed. The same remark will apply also to vegetable remains. 
It is evident that the newest of each series of formations 
will touch upon, and in some degree intermingle with the 
oldest of the succeeding series, and partake in some de- 
gree of the mutual characters. 
As the waters gradually decreased, and retired into 
their oceanic basons, the finer kinds of earthy matter 
would subside the last : and those saline substances that 
* I doubt about Pitch stonobelonging to this series. 
