No. 4.] CLAYPOLE — PRE-GLACIAL GEOGRAPHY. 219 



and it need scarcely be added that where there is fall enough for 

 a river to flow, there erosion will take place. It mnst moreover 

 be remembered that even allowing Dr. Newberry's supposition to 

 its full extent, the objection has no force, for it can only apply ta 

 the lowest points of the lake beds and the latest days of our pre- 

 glacial rivers. The geological destiny of every river is to cut 

 its bed down to the ocean-level, and time enough being given 

 every river will fulfil its destiny. The greater part of the lake- 

 beds, even on Dr. Newberry's supposition, must have been so far 

 above the old ocean as to give an ample fall, and in all but its 

 latest years the old river must have been equally high. It is 

 not surprising that a stream which, so far as we can judge, flowed 

 through that region for many ages, should ere its day of extinc- 

 tion came, have so far fulfilled its destiny as to leave what we 

 may call its death-bed but little elevated above the contemporary 

 ocean. It would be more surprising were the result otherwise. 

 On either view therefore little force lies in the objection. 



Similar arguments apply to Lake Michigan. Though the lake 

 is 900 feet deep, and the greatest known depth of the buried chan- 

 nel, ivhose hottojji has never been reached, is only 200 feet, yet 

 the latter is about 240 miles south of the middle of the lake, and 

 in the time of pre-glacial elevation the depth of the lake was di- 

 minished by 720 feet, and its outflow along the line previously 

 indicated through the State of Illinois not only possible but 

 probable. 



The above arguments seem fully to meet the objections urged 

 in the third volume of the Ohio Survey. Let us advance a little 

 further. Dr. Newberry agrees with the writer in admitting the 

 existence of the pre-glacial river to which allusion has been so 

 often made. He says (Geol. of Ohio, Vol. II, p. 77) : " Pre- 

 vious to the glacial period the elevation of this portion of our 

 continent was considerably greater than now, and it was drained 

 by a river system which flowed at a much lower level than at 

 present. At that time our chain of lakes — Ontario, Erie and 

 Huron — apparently formed portions of the valley of a river which 

 subsequently became the St. Lawrence, but which then flowed 

 between the Adirondacks and Appalachians, in the line of the 

 deeply buried channel of the Mohawk, passing through the trough 

 of the Hudson and emptying into the ocean 80 miles south-east 

 of New York. Lake Michigan was apparently then a part of a 

 river course which drained Lake Superior and emptied into the 

 Mississippi." 



