PLEISTOCENE SUBMERGENCE OF 4,000 FEET. 469 



he notes up to an elevation of 1,675 feet above the sea, and 175 feet above 

 the valley, along a tributary creek above St. George, West Virgiuia.^'^ 



At Nachvak, in Labrador, Dr. Robert Bell found beaches of great dis- 

 tinctness at 1,500 feet above the sea. Gravel and shingle terraces were also 

 found to an estimated height of 2,000 feet.f 



It has already been noted that the differential rise of the Iroquois beach, 

 north of the Adirondack mountains, amounts to six feet per mile, and that it 

 has there been lifted to a thousand feet. If this rise continues to the White 

 mountains, then the equivalent of the Iroquois beach may be found among 

 the terraces of the high valleys in that region. Its records may be preserved 

 still further northeastward on the drift-covered sides of Mount Katahdin in 

 Maine. Mount Desert, on the coast of Maine, rises to 1,500 feet,| and shows 

 remnants of coast action to its summit ; consequently it is too low to bear 

 records of the Iroquois shore, unless the warping of the earth's crust becomes 

 one of depression east of the Adirondacks. 



In Ontario, some of the high shores, referred to above, occur at elevations 

 of 1,000 feet above the Iroquois plain ; therefore their equivalents in the 

 northern Adirondacks should be looked for at about 2,000 feet above tide. 

 The beaches reported in Vermont by Professor Hitchcock at or below 

 2,300 feet, doubtless correspond to some high shore-lines of the Ontario penin- 

 sula. Upon the same basis these high beaches should be looked for at 3,000 

 feet in the White mountains, and at greater elevations on Mount Katahdin 

 in Maine. 



If we regard the gravels of the highlands of Pennsylvania as having been 

 formed at sea-level, then it would be reasoniable to look for their counter- 

 parts in New Hampshire, at elevations of over 4,000 feet on Mount Washing- 

 ton and to the summit of the drift (4,400 feet) on Mount Katahdin. These 

 conjectural estimates, based upon a possible uniformity, may aid in the cor- 

 relation of the topographic features of the mountain region of the east with 

 the lake region. 



Interpretation of the Evidence. , 



So far as relates to the northeastern portion of the continent, our observa- 

 tions on Neptunian phenomena have now been epitomized. An explanation 

 is necessary. That the pebbles of the beaches and the shore-lines were the 

 results of wave or current action no one questions, but there are differences 

 of opinion as to the conditions under which the waters moulded their coast- 

 lines. AVere these deserted shores constructed at sea-level, or were they 

 moulded in glacial lakes? These are the theoretical questions before us. 



*" Rounded Bowlders at High Altitudes," by I.C.White: Am. Journ. Sci., vol. XXXIV, 1887, 

 pp. 375-381. 

 t Rept. Geol. Surv. Can., 1885, DD, p. 8; and Bull. Geol, Soc. Am., vol. 1, 1889, p. 308. 

 i" Geology of Mount Desert," by N. S. Shaler: 9th Ann. Rept. U. S. Geol. Surv., 1888, p. 993. 



