STRUCTURE OF THE BASIN. 



123 



strata, of which there can not be less than 12,000 feet now remaining. 

 East of this line the upper strata are apparently denuded and the structure 



vr/s 

 -Outline map and £ 



I inn of the li;isin. 



is less well shown (see fig - . 8), largely owing to the covering of glacial 

 drift. In the southern arm, as is shown in Dr. Foerste's report, like 



FIG. 10. — Edward Hitchcock's 



ctiuii of tbb Carboniferous ; 



changes have taken place, and the incursion of the sea has done that which 

 is performed by sheets of sand and gravel in other parts < >f the basin. 



