J. 8, Newberry on the Formation of Cannel Coal 213 
decay ; a process, which, unattended by the sensible phenomena, 
heat and light, is however really a combustion id consists i 
the union of oxygen with their hydrogen to form water, with 
their carbon to form carbonic acid, and of their carbon and y- 
ogen to form carburetted hydrogen, &e. 
When vegetable matter is covered with wet earth or clay, 
these changes are both modified and retarded, and an interme- 
diate state, that of bituminization, is assumed by a portion o 
€ organic matter, 
Under water the changes terminating in decay go on still 
more slowly, and a larger portion of the vegetable tissue be- 
comes bituminized. 
_ The process of bituminization in such circumstances consists 
in the oxydation of a small portion of carbon—which escapes as 
carbonic acid,—of hydrogen to form water, the union of carbon 
and hydrogen to form carburetted hydrogen and other hydro- 
carbons, and the combination and removal of a portion of the 
ine carbonates, of nitrogen, &c., all of which go to make up 
the loss, which is relatively small. The residuary hydrogen and 
oxygen unite with a portion of the carbon to form bitumen, 
which closely resembles, physically and chemically, the resins 
produced by the vital functions of many plants. This bitumen 
we have evidence, not only in the great durability of wood when 
constantly submerged, but in coal itself. Beene 
strata except where the process of volatilization 1s 
complete, as plumbago and perfectly gasless anthracites, the 
Work of decomposition is constantly going on. To this, as to 
inary combustion, water is an extinguisher. 
; mines are commonly opened in this country by penetrat- 
ing the coal on some hill-side where it is not covered by water. 
' these circumstances a p ive change, both chemical and 
physical, is noticeable in the coal from its outcrop to the point 
Where atmospheric’ influences cease to act. Near the surface it 
'S friable, lustreless, and nearly destitute of gas, having much 
the appearance and character of decayed wood. As it is more 
deeply penetrated it becomes harder and more brilliant, and con- 
‘tains more volatile matter, till under water or a sufficient cover 
of incumbent rock, it is protected from the action of oxygen. 
