CHAPTER XVII 

 THE HISTORY OF NIAGARA RIVER 



THE RETREAT OF THE FALLS: 1886 



Gilbert's studies on the proglacial Great Lakes led him to look into the evolution of Niagara 

 River and its great cataract, and this fine subject became peculiarly his own. The logical 

 ingenuity with which he eventually combined many far-separated features of extremely unlike 

 character and arranged them all in an orderly sequence which led to the birth of Niagara River 

 and the retrogressive erosion of its gorge has hardly been excelled in the history of geological 

 science; and the marvelous manner in which the various features were found to fit to each other 

 when they were placed in the relations to which Gilbert assigned them is strong testimony for 

 the essential accuracy of his views. Some of the features that he thus linked up with their 

 proper associates had previously been fairly well explained in a local way by earlier investigators; 

 others had not been properly understood even as individual problems. It was left for Gilbert's 

 genius gradually to bring them all together in a comprehensive sequence and thus to make 

 clear the place that each held in the evolution of the region. As was usually the case with 

 Gilbert's studies, the field work was done by himself; he had no assistants. His methods were 

 moreover almost exclusively physiographic; they had little to do with stratigraphy and nothing 

 to do with paleontology or petrography; but they had everything to do with surface forms. 

 It is also noteworthy that this research was given a strongly quantitative flavor, at first with 

 regard to the erosion of the Niagara gorge and the recession of the Falls at its head, and later 

 with relation to the modern tilting of the Great Lakes region; this quantitative flavor as well 

 as the physiographic quality being strikingly characteristic of Gilbert's habit of thought and 

 treatment. Unfortunately, the results gained were announced only in many separate papers; 

 they were never brought together in the monographic form that they merited. 



Gilbert's first important contribution to the Niagara problem was made at the Buffalo 

 meeting of the American Association for the Advancement of Science in the summer of 1886, 

 when he analyzed the many factors on which the recession of the Falls depends ; thereafter 

 Niagara River was his subject in many other communications. The idea that the Falls were 

 worn back by the river was then already at least a century old ; in one of Gilbert's later papers 

 in which a historical review of the problem is given, it is noted that one McCauslin, who resided 

 at the Falls from 1774 to 1783, had even then found that everyone believed the cataract to have 

 been originally at the face of the upland escarpment which separates the higher basin of Erie 

 from the lower basin of Ontario, and back from which the 6-mile gorge has been cut; and this 

 early observer went so far as to propose and to discredit a curious method of determi n i n g the 

 rate of the Falls recession: "If we adopt the opinion of the Falls having retired sLx miles, and 

 if we suppose the earth to be 5,700 years old, this will give about sixty-six inches and a half 

 for a year, or sixteen yards and two-thirds for nine years, which I can venture to say has not 

 been the case since 1774 " ; but he does not go on to discover how old the earth must be if it has 

 witnessed a slower retreat of the Falls, much less does he inquire how much earth history had 

 elapsed before the Falls began! 



All through the following hundred years it seems to have been generally assumed that the 

 recession of the Falls had been at an essentially uniform rate; so that if the present rate were 

 determined, the age of the gorge could be calculated by the "rule of three." It was Gilbert's 

 peculiar merit to point out that the rate of recession depends on many factors, such as height 

 of plunge, volume of water, and resistance of rocks, most of which may have varied during 

 the excavation of the gorge; and although he did not then attempt to evaluate the effects of 

 these factors, he showed clearly that not until they are evaluated can the age of the gorge be 

 correctly determined. It may be recalled that an anonymous report of his communication in 

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