STEVENSON, GOAL BASIN OF DECAZEVILLE, FRANCE 263 



All of the beds along this line are to be taken as belonging to the 

 Bourran system and the Bourran coal bed extends northward beyond 

 Eiou Mort to be known as the Couche de Saint-Eoch. It is continuous 

 almost to the north end of the basin, but, though retaining considerable 

 thickness, it contains much shale, and, owing to the proximity of the 

 great deposits of both Campagnac and Bourran systems, its economic 

 importance at present is very small. 



At Decazeville, one reaches the area in which the Bourran bed has its 

 great development. The Bourran coal bed has escaped erosion at only 

 one locality in the eastern portion of the basin, where a small area re- 

 mained, south from the Firmy fault. The coal has been mined there 

 for much more than a century, but mining operations are almost at an 

 end, as the workings have reached the village under which the bed 

 passes. The decouverte is about 2 kilometers long by one fourth to one 

 half kilometer wide, and the coal has been removed to be replaced by 

 waste from the iron and steel works at Decazeville. As now exposed, 

 the coal at Firmy is compressed into a very close fold, whose axis passes 

 directly under the Firmy church. Only a small part of the bed is 

 shown, as rubbish covers the slope on both sides of the exposure. The 

 dips are abrupt, 50 to 60 degrees on the northwesterly side, but so 

 crumpled and distorted on the opposite side that no determination can 

 be made. Exposures on the road to Auzits show that the fold is double. 



The company's engineers give the thiclcness of the coal as about 50 

 feet. Blavier, as cited by Bergeron, gave the visible thickness in 1906 

 as 70 meters, and he believed that the mass exceeded 100 meters. This 

 exaggerated estimate was due to the fact that the workings at that time 

 exposed the face of the double fold. The dips become comparatively 

 gentle at a little way from the fold, so that wiiming of the coal by 

 decouverte was a simple and not expensive method, the amount of cover 

 to be removed being comparatively small. In this decouverte, one ob- 

 serves the unfortunate tendency of the Bourran coal to spontaneous 

 combustion, which has led to loss of vast quantities of coal in the several 

 decouvertes. The ignited mass gives ashes at the surface, coke lower 

 down and still lower a beautiful anthracite with no apparent trace of 

 porosity or weakness of structure. This charred coal cannot be utilized 

 by the company, as a very small proportion ruins the coke, but it is em- 

 ployed in manufacture of brick and in some other industries. 



Passing over to the principal area of the Bourran, one finds the coal 

 with only moderate thickness toward the southern border; and no mines 

 are in operation south from Cransac, because the thicker deposits are 

 available at the north. The bed forms a syncline, cropping out again at 



