COAL. 
463 
hundred feet in thickness. These layers of coal are 
situated at a place called Vert-Bois, to the north- 
west of the city ; and it has been remarked that the 
beds incline to the south, while those of a neigh- 
bouring mountain (to the south-east of Liege) dip to 
the north. Naturalists suppose these to be part of 
the same layers, which, passing under the large val- 
ley that separates this mountain from Vert-Bois, rise 
again on the opposite side, and thus take the form 
of a boat. 
There are different opinions among geologists re^ 
specting the origin of coal. Some suppose this 
combustible substance to be produced by the de- 
composition of the soft parts of the immense quan- 
tity of organized bodies, of which we find almost 
every where the solid remains. But unfortunately 
this conjecture, which appears so natural, is liable to 
several strong objections. One, is the presence of 
vegetables, scarcely decomposed, which are often 
met with in the middle of beds of coal. The others, 
the want of direct experiments to prove that orga- 
nized bodies give out bitumen during their decom- 
position. Without stopping to discuss these points, 
we shall merely give the general conclusions of na^ 
turalists as they are mentioned by Brogniart : 
1 . That coal was formed either at the same time, 
or after the existence of organized bodies. 
2. That this mineral, when first formed, was liquid, 
and of a great degree of purity. 
3. That the cause which produces this deposit is 
