OF THE PILLS OP ST. ANTHONY. 899 



It is tolerably well known where the Falls were, in the west 

 channel, in 1856. The Falls in the east channel have not 

 receded perceptibly since that date, while those in the west 

 channel have gone back about 500 feet, as already stated. In 

 general terms they were then abreast of Farnham and Lovejoy's 

 saw-mill, which stands on the west side of Hennepin Island. They 

 had a horseshoe shape, bending considerably upward in the centre, 

 and sweeping downward along either shore, their ends being nearly 

 opposite. If the statements of the earliest settlers are correct, the 

 line of the crest in the west channel met the island about 100 feet 

 below the lowest portion of the flat undisturbed portion of lime- 

 stone rock on which Farnham and Lovejoy's mill-dam is erected, the 

 mill itself having been originally erected in a little notch or jog in 

 the Falls, partly on the limestone and partly below the Falls, close 

 on the shore of the island. 



The most careful measurement ever made of the river between 

 Fort Snelling and the Falls of St. Anthony was conducted by Gen. 

 G. K. Warren. His maps have never been published ; but, through 

 the courtesy of Gen. A. A. Humphreys, a tracing of that covering 

 this interval has been obtained, which makes the distance almost 

 exactly eight miles. Prof. Rhame has made a series of triangula- 

 tions with the view of ascertaining as nearly as possible the amounts 

 of recession since Hennepin's and Carver's visits, and the dia- 

 gram (p. 897), drawn to scale, is based on his measurements. It is 

 evident that the interval between Carver's time and 1856 is the most 

 reliable datum, the statements of Hennepin not enabling us to 

 determine at what point in Spirit Island he saw the crest of the Falls. 

 Still, for the purpose of comparison, a point has been assumed on 

 Spirit Island, and from it measurements have been made. It is 

 presumed that Hennepin saw the Falls when they were near the 

 middle of Spirit Island, at a point, in the undisturbed limestone rock 

 of the island, in a large reentrant angle which runs from the top 

 of the limestone to the bottom on the east side, and 415 feet above 

 the line of the upper end of the stone piers supporting the lower or 

 iron bridge. That makes the recession between the discovery of the 

 Falls and Carver's visit 300 feet ; between Carver and 1856, 606 

 feet ; and the whole recession since Hennepin in 1680, 906 feet. 

 This gives us three rates of recession, viz. : — 



(1) Between Hennepin and Carver 3*49 feet per year. 



(2) Between Carver and 1856 6-73 



(3) Between Hennepin and 1856 5-15 „ 



The times required for recession from Fort Snelling would be 

 respectively :— (1), 12103 years ; (2), 6276 years ; and (3), 8202 

 years. The average of these is 8859 years ; but owing to the exact- 

 ness of the datum between Carver and 1856, it is likely that the 

 actual time involved would be more nearly expressed by taking 

 that only into the calculation. 



Now this, it is true, only expresses the time involved in the 



3o2 



