312 M. Levai-lou on the Environs, Sfc. 



them : they alternate with schists more or less penetrated 

 by carbonaceous matter. Among the rocks composing this 

 formation, there is one, among others, which is very remark- 

 able : it serves as a roof to a thin coal bed which occurs 

 near the surface. It is a white and very compact rock, con- 

 taining here and there only a few spots of mica. It might 

 be considered as one of the extreme limits in the series of 

 arenaceous rocks. 



This coal formation extends from hence into the commune 

 of St. Berain. Many pits are there opened. The coal 

 obtained is not of good quality ; but from the proximity of 

 the Canal du Centre, all the large coal is of advantage to 

 Chalons and Lyon. 



The gypsum formation, in the environs of St. Leger, rests 

 upon coal measures, and is covered by gryphite limestone.* 



The same relative position of those same mineral masses is 

 observed near Couches, 1 myriametre [about 7\ miles] to' the 

 W.N.W. of St. Leger. In fact, after having continually 

 travelled on these sandstones nearly to this town, where we 

 deviate a little to the left towards Chalancey, we soon meet 

 with the red and green marls resting on the sandstones, and 

 above them the gryphite limestone, in which the iron ore 

 occurs as a bed ; it is composed of hydrate of iron in very 

 small agglutinated grains, or a kind of ferruginous oolite. + 

 The marls do not appear there to be accompanied by gyp- 

 sum ; at least the presence of this mineral has not as yet 

 been ascertained. 



It should be remarked, that, from the observations of 

 Messrs. Lame and Thirria, the gypsum formation existing 

 at Decize, department of the Nievre, rests on the coal mea- 

 sures, and is covered by a gryphite limestone very analogous 

 with that of St. Leger. 



* Lias. (Trans.) 



t This is probably the iiifciior oohte above the lias. (Trans.) 



