GENERAL STATEMENT 237 



eastward into New England. The observational data and the calculated 

 results confirm the theoretic unity of the larger territory. 



As the Labradorian glacier reached only to Staten Island, the ice-front 

 recession through the Hudson-Champlain Valley represents all the time 

 involved in the removal of the ice-sheet, not only from all of New York, 

 .but from most or all of the Great Lakes area. The recession to Albany 

 corresponds in time to the recession from Salamanca to Syracuse. The 

 stages in the melting of the ice-sheet from New York have been shown in 

 a series of maps published by the New York State Museum (119, plates 

 32-40; 125,. plates 9-17). We have in the Hudson-Champlain Valley a 

 direct, complete, and evident record of the total amount of land uplift 

 during Pleistocene time for all of New York and the region of the Great 

 Lakes. Conversely, it is the record of the depth of submergence in the 

 sea at the close of glacial time. 



Outside the sea-flooded area the record is not so clear or full. In the 

 Erie and Ontario basins the tilted shorelines of the glacial lakes, when 

 compared and their deformations added, give us approximate figures. 

 The latest continuous beach of any particular lake registers only the 

 deformation subsequent to the extinction of the lake. The uplifting 

 which occurred during the life of the water body may be suggested by 

 the shifting of outlets or by the splitting of beaches ; but these records are 

 not always clear and the} r may be overlooked. Any possible uplift before 

 the initiation of the lake will, of course, not be recorded in its beaches. 



However, if the land uplift in any particular district was subsequent 

 to the un-icing of that locality, the glacial lakes which laved the receding 

 glacier front evidently register the earliest rising of the land. Many 

 years ago, in 1891, Mr. Upham made calculations, based on the several 

 glacial lake shorelines in the Erie and Ontario basins, with remarkably 

 accurate results (27, pages 261-262). This subject will be discussed 

 later. 



ISOBASES 



The accompanying map, plate 10, shows in isobasal lines the total 

 uplift of the land in Pleistocene time. Conversely, it shows the depres- 

 sion when beneath the load of the Labradorian ice-cap. 



If the reader refers to the map and diagram in the former article (127, 

 plates 10, 11), a difference will be noted between those maps and present 

 map which needs explanation. In the former diagram (plate 10) the 

 line representing the tilted uplift was drawn as a straight line, to be used 

 as a datum plane, in the absence at that time of sufficient data to plot 

 the line with its true curvature. In the sketch map (plate 11) the iso- 



