3oJ 



George E. Nichols, 



scoured out from the narrow-floored ravines through stream 

 activity ; but in the broad-floored valleys, as throughout the 

 Carboniferous lowland in general, it may still form, at least 

 locally, deposits many feet thick. Wherever these heterogeneous 

 deposits are exposed to the erosive action of the current, the 

 finer materials tend to be carried away, the coarser constituents 

 being left behind and forming what are here designated as 

 Boulder Plains- — areas covered with stones, mostly rounded, but 



Figure i8. — Boulder plain along lower course of Barrasois River. 



of all shapes and sizes (Figs. i8, 21). Where the stones are 

 uniformly small, they may well be referred to as Cobble Plains. 

 These stony plains commonly border the larger streams wherever 

 they flow through deposits of glacial drift. In flood time they 

 are submerged, but ordinarily, except for the small channel per- 

 manently occupied by the stream, they are uncovered. 



In contrast to boulder plains, which are a result of degrada- 

 tion, flood plains are a product of aggradation. They are best 

 developed along sluggish, old-age rivers, and at first thought 

 might not be expected to occur at all along swift, young streams, 

 like the majority of those in northern Cape Breton. But, on 



