l86 NEW YORK STATE MUSEUM 



found at successively lower intervals in the Champ] ain valley, and 

 an inclined plain drawn through them passes below the level of the 

 lake at Ticonderoga (Woodworth, 1905, p. 216 and pi. 28, line 

 M-N). This indicates a rate of tilting to the south during post- 

 glacial times of 4.1 1 1 feet to the mile.^ These shell fish are supposed 

 to have lived in from 100 to 300 feet of water (Woodworth, 1905, 

 p. 215). The present writer has considered the upper marine limit 

 at Crown Point as about 100 feet above the line of shells.^ It 

 would be, then, near the 200 foot contour. 



This postglacial elevation of the land has affected,, likewise, the 

 other shore lines above this so-called " upper marine limit " of 

 Woodworth. They now lie at proper intervals above the marine 

 shore line. Similar inclined planes have been used to correlate 

 these lake beaches and these are diagrammed by Woodworth on 

 plate 28 of this bulletin. He used a different set of criteria in 

 correlating them, however, because the low altitude of the land at 

 the time of their formation and its differential tilting since the 

 marine invasion cause them to lie in planes not quite parallel to 

 the so-called " marine " beaches, and they may have arisen at an 

 accelerated rate. 



The recent conclusions of Professor Fairchild at which he 

 arrived after a reexamination of all the data afforded, and after a 

 field consultation with Professor Goldthwaite of the Canadian 

 Geological Survey, are opposed to the hypothesis that these shore 

 lines above the so-called " marine " limit were formed by fresh 

 waters. He believes, as stated above (page 2), that they were 

 formed by waters of the Hudson-Champlain inlet. Their line of 

 tilting is less steep than that of the later marine line. This indicates 

 a faster rate of elevation since the marine episode than previous 

 to it. The rate of tilting of the higher shore line is about 2 feet 

 to the mile, while that of the lowest or marine is 4.41 1 feet to 

 the mile (Fairchild, 1913, p. 24 and Woodworth, 1905, p. 191), 

 while that of the lowest or marine is 4.411 feet to the mile (Wood- 

 worth, 1905, p. 206). 



Woodworth regarded the highest and earliest of these shore lines 

 as having been formed in a body of water south of a retreating 

 ice cliff, or possibly in marginal lakes. Fairchild regards them as 



1 See footnote, page 19, and Woodworth, igoS, p. 206. 



2 Peet, 1904, p. 626. "The level of marine fossils falls below the marine 

 level 60-80 feet at the north and not far from that amount at the south. 

 At Montreal the upper marine limit on Mount Royal is 40 feet above the 

 highest deposit of marine shells yet observed." 



