294 ANNALS NEW YORK ACADEMY OF SCIENCES 



inclined to believe that the eruptions came at different times. The rock 

 is a notable feature in the northern part of the basin, but it is not con- 

 fined to that area. Three islets of eruptive rock, in part andesite, are 

 seen north from Lugan, which are in line with an islet of andesite in the 

 northwestern corner, as well as with prongs of an "altered prophyritic 

 rock" projecting from the southern border near Lugan. Cross sections 

 by Bergeron, Jardel and Picandet as well as those by Saint-Martin show 

 that in approaching those islets from the east, the coal is turned up 

 toward the west. Saint-Martin's sections farther north and south, in 

 which the eruptive rocks do not come to the surface, show similar ar- 

 rangement of the coal beds. Along this line the eruptive rock is newer 

 than the Permian, since that system is involved in the folds. The com- 

 plicated structure of the basin probably dates from the issue of these 

 rocks ; the petty outcrops are only projecting portions of a great mass 

 below, continuous from the southern to the northern part of the basin. 

 For the most part, the local faults and other irregularities of bedding, 

 thought to be due to causes acting during deposit, have resulted merely 

 from movements of softer between harder beds during the final dis- 

 turbance. 



