QUATERNARY AGE. — CHAMPLAIN PERIOD. 545 



have generally a flat summit, because levelled oft 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 adjoining. Very often, there 

 are plains at one or more levels besides the upper, owing to sub- 

 sequent wear of the Champlain deposits by river action ; and, in that 

 case, the valley is bordered by a series of terraces. Such terraces 

 around lake basins have been significantly called benches. The accom- 

 panying 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. 



2. Distribution. -— The fluvial and lacustrine formations appear to 

 characterize all the river-valleys and lake-basins of the continent, over 

 the Drift latitudes, and also, to a less extent, those still farther south, 

 so that they may be said to have a continental distribution. The 

 fluvial deposit generally accompanies the whole course of a stream 

 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 Champlain 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. 



3. Diluvian Deposits. — The earlier stratified deposits were very 

 largely clayey, the counterpart of the bed of bowlder-clay among un- 

 stratified deposits, but differing in its distinct lamination. Clay-beds 

 were the prevailing kind about great lakes, and also along portions of 

 river valleys, where the waters were slow in movement ; and, in view 

 of their extent over the region on the north of Lake Erie, these lower 

 clay-beds have been designated by Logan the Erie clays. But, where 

 the waters were rapid, even the lower beds were sand or gravel ; and, 

 in a river valley, a deep deposit of laminated clay sometimes changes 

 laterally to sand, in the course of a few rods, showing that the river 

 had its eddies where clays were deposited, while making sand beds where 

 moving rapidly. These lower beds, in the region of the Great Lakes, 

 have sometimes, at or toward the top, local beds or patches of vegeta- 



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