QUATERNARY AGE. — CHAMPLA1N PERIOD. 



545 



and its tributaries, to the sources in the mountains, and fails only 

 where the stream is a steep mountain-torrent, or is bounded by lofty 

 walls of rock. A map showing the distribution of the formation over 

 the continent, in Drift latitudes, would hence be much like a map of 

 the rivers, the courses being the same for each ; the only exceptions 

 being that the minor bends of the rivers would be absent, and that the 

 breadths would be very much greater. The flood-grounds of some 

 large streams are now miles in width ; but, in the Cham plain period, 

 the waters often spread to three or four times the distance of any 

 modern flood, besides rising to the high level marked off by the upper 

 plain or terrace. 



2. Topographical features. — These formations, whether along river 

 valleys or about lakes, have generally a flat summit, because levelled 

 off by the waters. They stand at various heights, the top often one 

 or more hundred feet above the level of the river or the lake adjoin- 

 ing. Commonly, there are plains at several levels, in which case, the 



Fig. 941. 



Terraces on the Connecticut River, south of Hanover, N. H. 



valley is bordered by a series of terraces. Terraces around lake basins 

 have been significantly called benches. The accompanying sketch 

 (Fig. 941), from the Connecticut River valley, some miles south of 

 Hanover, N. H., represents the general appearance of the formation, 

 with its terraced surface. Up and down the stream, horizontal lines 

 may often be traced for miles, marking the limit of one or more of the 

 several terraces bordering it. Many villages in the vicinity of rivers 

 owe a large part of the beauty of their sites to these natural terraces. 



