Grove Karl Gilbert. 679 



covery that the ancient shorelines, which he had earlier 

 known in the Maumee valley, southwest of Lake Erie, 

 ascended to the northeast. This compelled him to give 

 up the idea he had originally entertained, that the lakes 

 had been raised by an upheaval of the land in the 

 St. Lawrence district, and to adopt Newberry's view that 

 the high-level lakes were enclosed by a retreating glacial 

 barrier. Intermittent attention to this problem resulted 

 in 1896 in a " History of the Niagara River, ' ' a most 

 luminous generalization, published in the Sixth Report of 

 the Commissioners for the [N. Y.] State Reservation at 

 Niagara. More formal study, when the Great Lakes 

 came to be an official assignment (1896-97), produced 

 a report on "Earth Movements in the Great Lakes 

 Region," published in the 18th Annual Report of the 

 Director of the Survey. 



In 1899, Gilbert visited Alaska as a member of the 

 Harriman expedition and there recognized the convinc- 

 ing evidence of intense glacial erosion that is given by 

 the much greater depths of the main fiord troughs than of 

 their lateral tributaries, for which it was he who sug- 

 gested the name of "hanging valleys." His observa- 

 tions are reported in a fine volume on Alaskan Glaciers, 

 where he brought forth the noteworthy idea that glaciers 

 which invade the sea rest so heavily on their trough floor 

 that no sea water can enter beneath to buoy them up ; 

 and that they therefore continue to press upon and to 

 erode their floor with their whole weight, even if six- 

 sevenths or more of their thickness is submerged. The 

 San Francisco earthquake was later the subject of study, 

 and following this came his last formal work, an exam- 

 ination of the conditions under which gravels have been 

 spread forth from hydraulic gold washings in California ; 

 this resulted in Professional Paper No. 86 of the 

 Survey, entitled "The Transportation of Debris by 

 Streams." During the progress of these two studies, 

 Gilbert was frequently at Berkeley, where he was a wel- 

 come ~guest of the hospitable Faculty Club of the L^ni- 

 versity of California, as he was also of the enterprising 

 "Sierra Club" of San Francisco during its summer 

 excursions in the mountains. 



The breadth of Gilbert's interests is shown by the many 

 topics on which he wrote besides those already enumer- 

 ated. They include, among others, barometric hypso- 

 metry, the percentage of success and error in weather 



