
268 B. N. A. BOUNDARY COMMISSION. 
especially by the existence of large areas which since the drift 
period have never developed systems of drainage valleys, and yet retain 
with little modification the irregular appearance of the original surface 
of the drift deposit, and are dotted with numerous ponds and lakes 
without outfall. The pre-glacial streams too, choked up along the edge 
of the third steppe by the drift of the Coteau, aud which have since 
been unable to clear their channels, give evidence of this kind. 
