220 Frank Carney 



nal suggestion, are the recently discussed buried channels of the 

 Hudson valley, channels brought to light in engineering projects 

 connected with the water supply of New York City.^ 



It has also been thought that the preglacial drainage of the 

 Great Lakes area reached the ocean as it does to-day. The con- 

 figuration of the present St. Lawrence valley precludes any such 

 hypothesis. Its originator so grants, but he explains that since 

 the close of the Wisconsin glacial epoch, tilting of the land has 

 locally lifted the floor of the St. Lawrence valle3% and that now 

 its altitude is much greater than formerly. That land tilting of 

 this nature has taken place in postglacial times is already well 

 established through a study of the deformed beaches of ice front 

 lakes. If the reconstructed drainage of the Great Lakes basin 

 reached the Atlantic through the St. Lawrence area, the amount 

 of land deformation required would certainly be beyond any con- 

 ception held by geologists. This plan of reconstructed drainage 

 has very few advocates. 



Others have shown how the Great Lakes, with the possible 

 exception of Lake Ontario, occupied depressions which pregla- 

 cially drained towards the Missisvsippi basin. This reconstructed 

 drainage is most generally accepted. Some differences of opinion 

 appear in details. One investigator hypothecates a former river 

 that followed, in general, the basins of the present Michigan and 

 Superior lakes ; another stream having its axis through Saginaw 

 bay, and with its tributaries draining most of what is now the 

 Huron basin and Georgian Bay; while the Lake Erie basin was 

 drained by another river, whose headwaters included part of the 

 Lake Ontario region. These three rivers had courses to the south- 

 west. No attempt has been made to work out any further de- 

 tails as to their southern courses. This same geologist hypothe- 

 cates another southflowing stream from the eastern end of Lake 

 Ontario's basin, reaching the Atlantic through the Susquehanna 

 system. 



Local warping. Deformati^^e movements of the earth's crust 

 have been known to so bow original horizontal rocks as to pro- 

 duce a basin in which drainage, accumulating from the adjacent 

 slopes, would form a lake. Where such a movement has made a 

 basin, a study of the rock attitude should reveal the fact. Apply- 



'■• J. F. Kemp, American Jourtial of Science, vol. xxvi, (1908), pp. 301-323. 



