CHAPTER XVIII. 

 THE CHAMPLAIN PERIOD (Continued). 



GLACIAL LAIvES WEST OF TIIK CONNECTICUT RIVER. 



THE GRANVILLE LAKE. 



As the ice retreated northwesterly, still sending great lobes down the 

 Connecticut and down the Westfield River, it abandoned the high valley 

 which occupies the whole middle of the town of Granville, while its Con- 

 necticut lobe still closed the outlet of this valley at the northeast corner of 

 the town and the gap of Munns Brook, which is cut so curiously through 

 the middle of the eastern riin of the valley. This rim is caused by the 

 greater durability of the vertical schists of which it is made, which strike 

 north and south and form an impassable barrier along the whole eastern 

 side of the town, except that it is cut asunder by this deep notch in its 

 middle, down which a road once ran. 



This broad valley, which extends across the whole length of the town 

 and a long way into Connecticut, was filled by a great body of sands, now 

 finely terraced down by brooks which run out of the basin on the north, 

 east, and south (g P, PI. XXXV, B). Its height is plainly determined by 

 its southern outlet, where the brook has a rocky bottom, and it is clear that 

 when the sands filled the basin the northeast and the east outlets (b*) must 

 have been closed, since, on being opened, the brooks which occupy them 

 cut down deeply through the sands before they reached the rocky bottom 

 of these outlets, proving that the latter were preexistent and deep enough 

 to have kept the waters at a much lower level if they had been open. 



THE NORTH GRANVILLE LAKE. 



Another lake of great extent stretches from Grranville into Blandford, 

 suiTounding Cobble Mountain (g P). Its coarse sands reach a gi-eat 

 depth. It was drained by the setting free of tlie South Brancli of the 



MON XXIX 38 593 



