6o /. W. SPENCER 



field. As the higher beaches have been found by all of us to indicate 

 the greatest amount of warping, we should not expect to find a 

 great amount in the altitudes of the Champlain marine deposits, 

 but we see these recurring at so many points to about 500 feet above 

 sea-level, that, upon examining their locations in the St. Lawrence 

 Valley, it is noticeable that they occur along segments of the circle, 

 roughly speaking, with the radii converging to the vicinity of the 

 focus found; while in receding toward Gaspe, New Brunswick, and 

 Nova Scotia the marine deposits rise only to lower and lower alti- 

 tudes. These data are well known, so that an undue demand on 

 the reader's patience need not be made by their repetition here. 

 So also with regard to most of the elevations on the Iroquois and 

 Algonquin beaches. Again, the eastern equivalent of the warp- 

 ing of the Iroquois, south of Lake Ontario, and in the Mohawk 

 Valley, supports the hypothesis of declining postglacial warping in 

 that direction, after passing the eastern end of Lake Ontario. 



The question of the location of the line of maximum post- 

 glacial elevation radiating from the region mentioned raises several 

 points in physical geography; one of these being the explanation 

 of the cause of the rise, as due to the disappearance of the glaciers, 

 for this locality was hardly the center of glacial dispersion. This 

 idea, however, is here thrown out for others to consider. 



Since these notes were written, the admirable paper of Professor 

 Goldthwaite on the " Isobases of the Algonquin and Iroquois 

 Beaches " has appeared. While the treatment of the postglacial 

 warping by isobasic lines is scarcely other than a different mode 

 from determining the mean rise in the various triangles, yet each 

 has a significance of its own. The isobases indicate a regional 

 rise toward the Laurentian axis. The triangles carried this rise 

 to the " Height of Land " and show the locus of maximum rise 

 north of the Great Lakes. 



Note on the Accompanying Map 

 The triangles about Lake Ontario are based on the instrumental measure- 

 ments of the Iroquois beach, at the places on the map; those east of Lake 

 Huron, on the measurements of the Algonquin beach. Height, at Rome and 

 Sodus after Fairchild, of Holland Landing and Rosedale (in place of my Kirt- 

 vill) after Goldthwaite. The other points are from my own surveys. 



