478 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



whose results, chiefly from the paleobotanist's standpoint, were pre- 

 sented in many memoirs. Two papers, pubHshed by the Interna- 

 tional Geological Congress, may be accepted as summarizing his 

 conclusions. 



According to Gruner, the succession, ascending is : 



Breche de la base ; Stage houiller de Rive-de-Gier ; fitage sterile 

 de St. Chamond ; fitage houiller inf erieur de St.-£tienne ; fitage 

 moyen de St.-£tienne ; fitage superieur de St.-fitienne ; Stage sterile, 

 or Permo-Carboniferous of Grand'Eury. 



These outcrop in concentric curves, now broken and distorted by 

 faults. The basin embraces about 80 square miles ; the second and 

 third stages occupy not far from nine tenths of the area, if they exist 

 under the higher divisions ; the fourth is present in almost one half 

 of the basin ; the fifth, in less than one fourth, while the sixth and 

 seventh are in less than one twelfth. 



The Breche is a confused mass of angular fragments, slides from 

 primitive rocks, surrounding the basin, and nature of the fragments 

 differs according to locality, granite prevailing at some, gneiss at 

 others. It is from 20 to 200 meters thick and the top is at 15 to 20 

 meters below the lowest coal seam. 



The Rive-de-Gier, consisting of sandstone with some shale, is 

 100 to 120 meters thick and has four workable coal seams, as well as 

 several thin streaks. The highest. Grand Masse, is divided by a 

 parting of white sand, known as Nerf blanc and not more than 10 

 inches thick. Coal from the lower bench is hard, dull, contains 

 much oxygen, is good fuel for grates and is termed " rafiford " ; that 

 from the upper bench, termed " marechal," is tender, brilliant, has 

 less oxygen than the other and is excellent for gas and coke. In 

 the western part of the area, coal from both benches has less volatile 

 than at the east and, in the last concessions, it becomes anthracitic 

 at depth of 500 to 600 meters. At the eastern limit of the Rive-de- 

 Gier, the Grand Masse is from o to 0.50 meter thick ; but it increases 

 toward the west and becomes 15 meters at Grand'Croix. It thins 

 away at the borders of the area. The roof is sandstone ; during its 

 deposition, the coal suffered much from erosion, all having been re- 

 moved at numerous places ; the mur is tender, often swells and re- 

 places much of the coal. The seam, les Batardes, 35 meters lower. 



