218 On tfo. Surfact Geology of tin Basin of the 



lower than the Mussel Shoals, it must be Bomewhere connected 

 with the deep channel < »t' 1 1 10 lower river. 



It Bhonld be Baid, however, thai it by no means fellows that 

 where an old earth-filled channel passes around the rocky bar- 

 rier by which the navigation of our rivers is impeded, it will 

 be mosl convenient and economical to follow it in making 

 a canal to pass the obstacle, as the course of the old channel 

 may be so long and circuitous that a short rock cutting is 

 aper and better. The question is, however, of sufficient 

 importance to deserve investigation, before millions of dollars 

 are expended in rock excavation. 



If it is true that our great lakes can be connected with 

 each other and with the ocean, both by the Hudson and Mis- 

 Bissippi, by ship canals, — in making which no elevated sum- 

 mits nor rock barriers need be cut through, — the future com- 

 merce created by the great population and immense resources 



of the basin of the great lakes may require their construction. 



3d. Opon the glacial surface we find a series of unconsoli- 

 dated materials generally stratified, called the " Drift deposits." 



I If these, the first and lowest are blue and red clays (the 

 i clays of Sir W'm. Logan), generally regularly stratified in 



thiii layers, and containing no fossils, but drifted coniferous 

 wood and leaves. Over the southern and eastern part of the 

 lake basin, these clay- contaiu no boulders, hut towards the 

 North and West they include scattered Btones, often of large 



f'.yj- : while iii places beds of boulders and gravel are found rest- 

 ing directly on the glacial surface. 



[u Ohio, the Erie clays are blue, nearly 200 feel in thickness, 



and reach up the hill-sidee more than l'i»<> feet above the present 

 surface of Lake Erie. On the shores of Lake Michigan these 



claw- are in pari of a red Color, showing that 1 1 n • \ have keen 



derived from differenl rocks, and they there include great 

 numbers of Btoni 



On the peninsula between Lake Erie and Lake Huron the 

 Eri( fill the old channel which formerly connected these 



