RATE OF RECESSION 81 



rate of the final ice retreat between localities 24 and 28 amounted 

 to 328 feet (100 m.) a year. Further investigations are needed 

 to reveal the actual conditions. 



Rate of Recession in the Middle Zone 



In northern Massachusetts the amount of the annual recession 

 was 193 feet (59 m.). The rate of retreat increased until the ice 

 edge reached the Bellows Falls region, whereupon it decreased 

 again, judging from the halt of the ice edge at Claremont 

 and from results obtained in the Merrimac Valley. When 

 fastest, the recession reached approximately 370 feet (113 m.) 

 a year. 



In the Merrimac Valley the retreat was a little slower than 

 in the Connecticut, probably because it was situated closer to 

 the sea, where the sky was more clouded. The highest rate was 

 reached a little north of Concord. The subsequent retardation 

 was rather noticeable. 



Oscillations in the Lake Winnepesaukee Region 



In the Claremont-Lake Winnepesaukee zone the ice edge 

 again halted and readvanced. At locality 41, in the Connecticut 

 Valley, four feet of coarse gravel with several boulders a foot 

 in diameter overlie discordantly a thick deposit of varve sand 

 which represents more than 50 years (see p. 22). The gravel is, 

 no doubt, outwash deposited during a readvance of the ice edge. 

 Around Lake Winnepesaukee till in doubtless its original position 

 frequently overlies varve clay, marking oscillations of the ice 

 border (Upham, 1878, p. 131). A few such localities were 

 visited by Goldthwait and the writer. At Clay Point, 3 miles 

 southwest of Wolfeboro, at the southeastern end of the lake, 

 the varve clay, which according to Upham is at least 15 feet 

 thick, is now covered by talus. The original position of the 

 overlying till is obvious. At Weirs, on the western side of the 

 lake, a third of a mile north of the railroad station, a 30 to 40-foot 



