76 THE BUTTERFLIES OF NEW ENGLAND. 



had already in preglacial times sunk their channels well down towards the 

 base-level, the side streams had become very numerous and the valley-slopes 

 had widened out as the intervening hills wasted away ; and a rolling, 

 hilly surface, rising in places to mountains of moderate heights, has thus 

 been produced. It is not desired to affirm in this description that the earlier 

 erosion had produced a perfect plain ; considerable inequalities doubtless 

 remained at the time of general elevation ; nor that all our rivers are new- 

 born ; the larger ones may still follow the course of their ancient predeces- 

 sors ; nor that the elevation was sudden, single or uniform ; it was more 

 probably progressive and uneven : but it can hardly be questioned that the 

 preparation of our topography required some such process as is here sketched. 

 Pennsylvania has had a similar history ; but there the relatively simple and 

 orderly structure of the rocks compels a correspondingly simple and orderly 

 arrangement in the present topography. In New England, the harder and 

 higher parts of the old surface presumably still remain in the mountains 

 and hills of to-day, but the rock structure which determined the arrange- 

 ment of these parts is so complicated that a simple and systematic classifi- 

 cation of the present topography is impossible. Moreover, New England 

 has been heavily glaciated in comparatively recent times, and although ice 

 cannot be held responsible for the production of the greater topographic 

 forms, it has been directly and indirectly most potent in fashioning the 

 details of form which are familiar to us on every side. Before considering 

 these, the larger physical divisions of New England may be briefly de- 

 scribed. 



There are five divisions easily recognized. The Hudson-Champlain val- 

 leys, which mark the natural or physical boundary of New England on the 

 west ; the Green Mountains and the associated ranges on their western 

 slope ; the great valley of the Connecticut Kiver ; the White Mountains, 

 descending to a plateau with occasional mountains in southern New Hamp- 

 shire, and continued as a dissected plateau in Massachusetts and Connecti- 

 cut, while to the northeast the disconnected mountains of northern Maine 

 may be placed in the same group : and finally the lower coastal slope from 

 Rhode Island north-eastward. 



The Green Mountains may be conveniently taken first. Their main 

 range consists of gneissoid rocks, trending a little east of north through the 

 western parts of Connecticut, Massachusetts and Vermont. South of the 

 latter state, they form a dissected plateau, under 2500 feet in height : farther 

 north, the elevation increases, and the range is dominated by well marked 

 summits, four of which rise over 4000 feet : Jay Peak, 4018 ; Mansfield 

 Mountain, 4389 ; Camel's Rump, 4077 ; and Killington Peak, 4221. It is, 

 curiously enough, only in the northern, higher portion of the range that it 

 is traversed by rivers ; the Winooski and the Lamoille, flowing from east 

 to west, open low passes (about 400 and 500 feet) for transverse roads, 



