THE DATE OF THE GLACIAL PERIOD. 557 



Having thus established the post-glacial origin of the 

 gorge below the Falls of St. Anthony, the next point was to 

 determine the rate at which the recession has been proceed- 

 ing. Fortunately, upon this point an abundance of evidence 

 is available. The falls were first visited and described as 

 early as 1680 by the Jesuit missionary Hennepin. His de- 

 scription is found in the Amsterdam edition of his works, 

 printed in 1704. The falls were again visited in 1766, eigh- 

 ty six years later, by Carver, another Jesuit missionary. In 

 addition to his description this traveler made a sketch of the 

 falls, which was engraved to accompany his travels, published 

 in London in 1778. Subsequent travelers who describe it 

 are Major Z. M. Pike, in 1805 ; Major Stephen S. Long, in 

 1S17 ; Schoolcraft, in 1820 ; Professor William Keating and 

 Mr. Beltrami, Eev. W. T. Boutwell and Schoolcraft, in 1832 ; 

 and Mr. Gr. W. Featherstonhaugh, in 1835. In addition vari- 

 ous artists have gathered descriptions of the falls as they ap- 

 peared in 1842, 1848, 1853, and in 1857, and daguerreotypes 

 were taken in 1851; while in 1853, before the erection of saw- 

 mills, Mr. J. W. Bond gave a careful description of the falls 

 as they then existed, and numerous living witnesses fix their 

 position in 1856, when artificial changes were introduced, 

 which so modified the rate of recession as to disturb further 

 calculation. The period, then, during which evidence is avail- 

 able for calculation is that between Hennepin's visit in 1680 

 and the year 1856 — one hundred and seventy-six years. The 

 descriptions are so minute that Professor Winchell is able to 

 fix beyond doubt the various stages of recession between 

 these dates. 



In 1680 the falls were near the south end of Hennepin 

 and Spirit Islands, not far above the present Tenth Ave- 

 nue Bridge. In 1766, at the time of Carver's visit, the falls 

 had receded about four hundred and twelve feet, and were at 

 Carver's Island. In 1856 the west falls were about five hun- 

 dred feet below their present position, which is now made sta- 

 tionary by artificial means. According to Professor Winchell, 

 the recession from 1680 to 1766, between Hennepin and 



