Spencer.] 66^ [March 18, 



Depths of the lakes cannot be accounted for by the relatively higher elevations 

 of northern latitudes. In the first place, Lake Ontario has a bottom very 

 much deeper (below the sea), than even the deepest sounding in Lake Su- 

 perior, or 500 feet below sea-level. 



If a suflScient elevation did occur, it would require to be local, or to ex- 

 tend far to the southward. That it was not local appears from the general 

 dip of rocks in which it lies. 



However, any continental elevation or subsidence occasioned by the 

 change of the centre of gravity of the earth, such as that by the great ac- 

 cumulation of ice in the polar regions, would be equal to the elevation or 

 subsidence at the pole multiplied by the sine of the latitude. From this 

 we find that if the elevation at the poles were a thousand feet, the differ- 

 ence between the elevation or subsidence of the northern end of Lake 

 Huron and the Dundas valley, would be equal to only about 40 feet. Even 

 were the ice-cap uniform around the poles, it has never been calculated 

 that it was sufficient to cause a polar difference of 3000 feet of level, which 

 at most would effect the relative levels of the northern end of Lake Huron 

 and the southern latitude of Ontario to no greater extent than 120 feet. 

 Again, it is shown by Prof. Whitney, that no ice cap occupied north-western 

 America, and by the author of "Fire and Frost" (see Q. J. G-. S.), that the 

 ice-belt is only known to have surrounded the region of northern Atlantic. 

 The greatest changes of level by the accumulation or removal of ice would 

 thus be occasioned along the north-eastern margin of America in the 

 region of the Appalachian and Laurentian mountains. If the continent 

 continued high during the Ice Age, the coastal ranges would cut-off most 

 of the moisture, and thus greatly lessen the thickness of any ice sheet over 

 the region of the great lakes, if it ever did exist. This is exactly the state 

 of the ice in Grinnell land (Lat. 81° K). Messrs. Fielden and Ranee, ob- 

 served "the paucity of glaciers, and the non-existence of the icecap," 

 (Q. J. G. S., No. 135), and state that no glaciers descend to the level of the 

 sea, as on the Greenland coast or Hall basin. 



The idea of the lake basins being greatly effected by oscillations must be 

 abandoned, except so far as the whole area was subject to a more or less 

 uniform change acting proportionably on the eastern and central parts of 

 the continent. Even then, the change was far too little to explain the 

 depths of these waters. Another evidence against the irregular changes 

 of the lake region is that, at the close of the Ice Age we have terraces in 

 Canada a thousand feet or more above the sea, and at various levels all the 

 way to the present surfaces of the waters. Terraces or ridges occur at 

 similar heights in our country, Ohio, New York and elsewhere. In a sub- 

 sequent paper the writer hopes to show the relation existing between these 

 old beaches, terraces and kames, deposited when our three lakes formed one 

 common body of water. That this water had numerous outlets, as the con- 

 tinent w^as rising, has been pointed out by the Geological Survey of Ohio, 

 to say nothing of the outlets referred to by the Surveys of Pennsylvania 

 and Canada. At only a comparatively few levels did the waters seem to 



