21f> On the Surfaa Geology of tin Basin of th< 



level of the lake ttlUSl have Once lieei) at least LOO feet lower 

 than now. 



The bottom of the excavated channel in which Onon- 

 daga Lake is situated, and the Salina salt-wells bored, is at 

 Least 414 feet below the surface level of the lake and 50 feet 

 below the sea level, (Geddes. Trans. New York State Agri- 

 cultural Society, L859. | 



The "Id channel of the Oenesee River at Portage, described 

 by Prof. Hall in the Geology of the 4th District of New York; 

 the trongh of the Hudson, traceable on the sea bottom nearly 

 l"i> miles from the present river mouth ; the deeply buried bed 

 of the Lower Mississippi, are additional examples of the same 

 kind ; while the depth to which the Golden Gate, the Straits 

 of Carquinez, the channel of the lower Columbia, the Canal de 



Haro. II 1's Canal, Puget Sound, Arc, have been excavated, 



indicates a similar (perhaps simultaneous) elevation and erosion 

 of the Western coast of America. 



The tails of the Ohio — formed by a rocky barrier across the 

 Stream — though at first sight seeming to disprove the theory of 

 a deep continuous channel in our Western rivers, really afford 

 no argument against it, for here, a- in many other instances, 

 the present river does not follow accurately the line of the old 

 channel below, but runs along one or the Other side of # it. In 

 the case of the Louisville tails the Ohio nTns across a rocky 

 point which projects into the old valley from the north side, 

 while the deep channel passes under tin- lowland on the south 



side, on part <>f which the city of Louisville is built. 

 The importance of a knowledge of these old channels in the 



improvement of the navigation of our larger rivers is obvious, 



and it i- possible it would have led to the adoption of other 



means than a rock canal for passing the Louisville falls, had it 



been possessed by those concerned in this enterprise. 



I ventured to predict to Gen. Warren that an old tilled up 



channel wonld be found passing around the Mississippi rapid,-, 

 and his examinatione have confirmed the prophecy. 1 will 



