348 EARTH FEATURES AND THEIR MEANING 



more drain to the Mississippi and the Gulf. Upon the basis of 

 his measurements, Gilbert ventured the prophecy that the first 

 high-water discharge into the Mississippi should occur in from 

 five hundred to six hundred years, and for continuous discharge 

 in fifteen hundred years. In twenty-five hundred years Niagara 

 Falls should at low water stages be dry from this cause, and in 

 thirty-five hundred years it should have become extinct. 



This prophecy, emanating from a high scientific authority and 

 relating to changes of such profound economic and commercial 

 importance, has been often quoted and has taken a firm hold upon 

 the popular imagination. Obviously, it depends upon the now 

 exploded theory that the lake basin has been canted as a plane 

 and that the axis of uptilt lies somewhere to the southward of 

 the lake region, or, in any event, to the southward of the present 

 Port Huron outlet. We know to-day that instead of being uni- 

 formly distributed over the entire lake region, the uptilting goes 

 on at a much higher rate within the northern .areas, and that 

 since the early stage of Lake Whittlesey the hinge line of uplift 

 has been steadily migrating northward with the retreat of the 

 ice and is now well to the northward of the present outlet. There 

 is, therefore, no known uptilt of the district which separates 

 the present from the former Chicago outlet, and there is no ap- 

 parent natural cause which should result in the reoccupation of 

 the old outlet to the Mississippi. The prophecy must be regarded 

 as one that has been outgrown with the progress of science. 



Geological evidences of continued uplift. It has recently 

 been claimed, on the basis of a reexamination of Gilbert's study 

 of the lake gauge records, that his methods are open to serious 

 criticism and that in reality the figures afford no evidence of con- 

 tinued uplift of the region. However this may be, there are not 

 lacking geological evidences which do not admit of doubt, and 

 these are in a striking way confirmatory of the latest conclusions 

 upon the manner of the recent uplift. 



If our conclusions have been correct, the several lake basins 

 should now be behaving in different ways as regards the changes 

 upon their shores. If it is true that the lines of greatest uptilt 

 run north-northeasterly, there should be, speaking broadly, a 

 " spilling over" of waters upon the south-southwesterly shores 

 and a laying bare of the north-northeasterly shore terraces of the 



