OF ARTS AND SCIENCES. 133 



" In 1823, Governor Cass instituted a series of experiments, at the 

 head of Green Bay, to determine the changes in the water-level. These 

 observations extended from the 15th of July to the 30th of August, 

 and from them he infers ' that the changes in the elevation of the 

 waters are entirely too variable to be traced to any regular permanent 

 cause, and that consequently there is no perceptible tide at Green Bay 

 which is the result of observation. And such, it appears to me, is the 

 result of calculation, when the laws that regulate solar and lunar attrac- 

 tion are taken into view.^ * 



" In the summer of 1834, an extraordinary retrocession of the 

 waters took place at Sault St. Marie, the outlet of the lake. The 

 river at this place is nearly a mile wide, and in the distance of a 

 mile falls 18.5 feet. Its bed is sandstone, and, except in the immediate 

 channel, the average depth of water is two and a half feet. The 

 phenomenon occurred about noon. The day was calm, but cloudy. 

 The water retired suddenly, leaving the bed of the river bare, except 

 for a distance of thirty rods, and remained so for nearly an hour. 

 Persons went out and caught fish in the pools formed in the depressions 

 of the rocks. The return of the waters is represented as having been 

 very grand. They came down like an immense surge, and so sudden 

 was it, that those engaged in catching fish had barely time to escape 

 being overwhelmed. 



" A similar phenomenon occurred twice on the same day in the lat- 

 ter part of April, 1842. The lake was free from ice, and no wind was 

 prevailing in the vicinity. 



" A few years previously, the precise period my informants could 

 not designate, the current between the foot of the rapids and Fort 

 Brady, which usually flows at the rate of two and a half knots 

 an hour, was observed to set back. The water rose two feet or 

 more,, and the rate of the back-current was estimated at two knots an 

 hour. Some of the soldiers at the fort, in order to satisfy themselves, 

 jumped into a boat and rowed into the stream, when they found the 

 current bearing them towards the foot of the rapids. How long this 

 continued, my informants could not designate. A strong wind was 

 prevailing from the south, but it was never before known to have 



* Remarks on the Supposed Tides and Periodical Rise and Fall of the North 

 American Lakes, by Major (now Brigadier-General) Henry Whiting, Jlmeriran 

 Journal of Science, Vol. XX., Part II. fc'ee also a paper by General 11. A. S. 

 Dearborn, Ibid., Vol. XVI. 



