No. 4.] CLAYPOLE — PRE-GLACIAL GEOGRAAHY. 217 



lu this connection it must be borne in mind that the theory 

 which Dr. Newberry is here criticising is founded on the fact, 

 generally admitted by geologists, that before the glacial era and 

 at the time when this old river existed, the relative levels of land 

 and sea were not the same as now, but that the laud was higher, 

 especially to the northward. Of this it is scarcely necessary to 

 adduce proof (see Dana's Manual, 1874, p. 540). Prof. New- 

 berry himself says (Geol. of Ohio, Vol. I, p. 44): "The rocky 

 bottoms of these gorges," in N. E. Oliio, " are deeply buried, 

 and the erosion which produced them began before the ice period 

 and was mostly accomplished during an interval of continental 

 elevation." Again (p. 172): "This excavation was anterior to 

 the drift period, when the continent ivas raised several hundred 

 feet higher than noic'' Again (p. 433) : "It is easy to see that 

 the erosion " of Mill Creek valley in Hamilton Co. " could not 

 have been effected under existing conditions. It can only be ex- 

 plained by a higher altitude of the continent." Again (Vol. II. 

 p. 6) : " At the commencement of the ice period this continent 

 must have stood several hundred feet higher than now." 

 - Facts gathered from North American and European geology 

 show that the elevation was not uniform but increased towards 

 the north, and the only assumption in the paper already alluded 

 to was that this northward elevation was at the rate of three feet 

 per mile. Now if this estimate be applied to Lake Huron and 

 the buried channel at Detroit, we have the following results : — 

 The central part of Lake Huron then lay about 540 feet higher 

 than now, or 260 feet below the present surface. The buried 

 channel at Detroit has been explored to the depth of 200 feet, 

 but its bottom has never been reached. Dr. N. says (Vol. II, 

 p. 13) : "Its greatest depth is unknown." This places the bed 

 of Lake Huron at the time in question only 60 feet below the 

 bottom of the deepest known boring (not the real bottom) in the 

 Detroit channel, and removes all serious difficulty from this part 

 of the subject. 



A similar argument will meet the objection urged in the case 

 of Lake Erie and quoted above. Lake Erie lying to the south 

 of Lake Huron, has been relatively less depressed since that time 

 and may actually have then been more deeply eroded than the 

 latter. 



3rd. " Lake Ontario is again a deep basin, being 450 feet deep, 

 with a surface level of only 234 feet above the ocean. Every- 



