188 PROCEEDINGS OP THE AMERICAN ACADEMY. 



supposed ice-dammed lake the terraces will be approximately continuous 

 except wliere tlte ice stood. On the drift barrier hypothesis it was very 

 difficult to explain how the terraces remained while the barrier was 

 removed, but the ice-barrier would disappear by simple melting, and 

 therefore the terraces would remain in nearly their initial form after the 

 retreat of the ice and removal of the water. The upper terrace level 

 would correspond in elevation with the height of the col over which the 

 lake discharged. This relation to the col has been worked out in con- 

 siderable detail in the study of the Great Lakes.* A reliable geologic 

 criterion is the occurrence of marine shells, which are found in marine 

 beaches but not in ice-dammed lake terraces. 



Examples. Raised beaches are found in Ireland on the north coast, in Killary 

 harbor, along Kenraare and Glengarriff bays, and elsewhere, according to Mr. 

 HuU.t 



For the raised beaches of Great Britain reference will be made to the papers by 

 the following authors : Ansted, Cliambers, De la Beche, A. Geikie, J. Geikie, God- 

 win-Austin, Prestwick, Richardson, Trevelyan. 



Tlie literature on Scandinavian X raised beaches is extensive, and there are manj' 

 fine examples of fading elevated shorelines upon that coast. The features do not 

 show distinctly enough upon the topographic maps for purposes of illustration. 



Old beaches at various levels above the water of Pechora bay in the Great 

 Tundra region of northern Russia appear to be former shorelines. § Mr. Jackson 

 does not mention less perfect terrace forms the further he went from the present 

 shoreline, but he proved the progressive stages of uplift by the less perfect preser- 

 vation on the more elevated beaclies of the pine tree trunks, which he considers as 

 brought down by the Pechora river. 



There is a former shoreline near Ogunquit, Maine, and also farther to the north- 

 east, upon which little work has been done since uplift. 



There is an 800 foot cliff six miles east of San Roque point. Lower California, 

 which should be examined in tiie field to determine whether it is a former sea cliflF 

 or not (H. O., 1208). 



Another case suggestive of uplift is seen in Santa Rosalia bay. Lower California 

 (H. 0., 1100, 1193). The lack of more accurate information about this region 

 makes it impossible to use it as surely showing uplift. 



Cliffs 75 feet high are seen along the Sonora coast, Mexico, near the mouth of 

 the Colorado river. They are so distinct as to indicate a recent elevation (H. 

 O., 800). 



* See papers by Fairchild, Gilbert, Lawson, Leverett, Newberry, Schott, Spen- 

 cer, Taylor, Upham, and Warren. 



t Physical Geology and Geography of Ireland, 1878, 107 ; see also paper by 

 Kinahan. 



X See pp. 158-160. 



§ F. G. Jackson, The Great Frozen Land, Macmillan & Co., 1895, 129, 262. 

 Map. 



