462 
COAL. 
cially the rich mines of Forez and Auvergne ; but 
it must also be remarked, that we find them ab- 
solutely enclosed in earths of a secondary forma- 
tion, such as those of Flanders and the mines of 
our own country. A circumstance mentioned by 
Patrin, which deserves to be attended to, is this : 
the beds of coal in these mines are always separated 
from each other by free stone and slate, sometimes 
of an enormous thickness, although it often hap- 
pens that nothing is to be found in the neighbour- 
ing!: earth which can contribute to the formation of 
o 
these stony layers. This almost amounts to a de- 
monstration that they are immediately produced by 
a chemical combination of nature, and not by any 
accumulation of pre-existent materials. 
Layers of lime-stone also occur between beds of 
coal, but always (I believe we may say without ex- 
ception) they are lined both at top and bottom with 
slate. All the calcareous ridge on the French side 
of the Alps contains beds of coal enclosed in the 
chalk, sometimes mixed with shells. A great num- 
ber of these beds have been discovered, and several 
worked from Lower Provence to the mountains of 
Meillerie, on the lake of Geneva. Several, and 
especially those of the intermediate countries, are 
noted for their extraordinary elevation above the 
surface of the sea. Those of Provence occupy a 
space of ten leagues in length from the south- 
east to the north-west, from Nans to Gardonne, near 
Aix. They are at the foot of great mountains, in 
hills composed of alternate layers of chalk and clay; 
