Coal Measures of Axeyron. gl9 



often none at all. Its inclination is not sensible except to- 

 wards its point of contact with the coal measures ; the beds 

 there become inclined from their previous horizontal posi- 

 tion, and acquire a dip of from 30° to 40°. 



Towards Severac-le-Chateau some limestone strata contain 

 veins of lignite (true jet) of little thickness, and not con- 

 tinuous enough to be worth working. The coal formation is 

 hounded on the S. by primitive rocks, on which it rests. 

 The rocks are composed of gneiss, the beds of which, not 

 very distinct, incline to the N. Proceeding S. the gneiss is 

 replaced by granite, which constitutes the central and ele- 

 vated chain of Levezon, separating the basin of the Aveyron 

 from that of the Tarn. 



The predominant rock of the coal measures is the true 

 coal measure sandstone, in beds of more or less thickness, 

 more or less regular^ but always inclined towards the N. or 

 nearly so. This sandstone is sometimes large grained, but 

 most commonly fine-grained. Though very hard to be 

 worked, it speedily decomposes in the air, loses its hardness, 

 and becomes of a yellowish colour on the surface. It some- 

 times alternates with micaceous sandstone, and sometimes 

 retains impressions of ferns and reeds. 



These impressions also occur in the argillo-bituminous 

 schists, which, in various points of the formation, accompany 

 the coal beds, either as a roof or floor, or dividing the coal- 

 beds themselves. 



Besides the schist, small veins or nodules of soft clay, 

 sometimes schistose, are found on the sides or in the inte- 

 rior of the coal beds. 



Lastly, the sandstone contains beds of coal, which, in 

 different points, vary as to thickness, inclination, and quality. 

 Their dip is the same as that of the sandstone. 



The number of coal beds observed at different points 

 varies from one place to another; it is the same with their 

 tnode of occurrence, thickness, and quality. 



