214 On the Tides in the great North American Lakes. 
- During a residence of nine years onthe straits of St. Mary, near 
the foot of Lake Superior, I have remarked that the waters of those 
straits, and of Lake Superior, are particularly exposed to the influ- 
ence of winds, which, for the greater portion of time, prevail either 
up or down the lake and the straits, thus subjecting them to an influ- 
ence in the direction in which they are susceptible of being most at 
fected by currents of wind. The effects are, a swelling in the wa- 
ters at the point opposite to that at which the force is put in motion; 
and a recession of the waters whenever this force is abstracted. The 
rise and fall thus produced, have much of the appearance of a tide. 
The waters often overflow the banks; and they may recede, and 
again overflow the same portions of shore, twice, or oftener, during 
the same day. : es 
Owing to counter currents of air, either in the higher or lower stra 
ta of the atmosphere, or to positive changes in the current of the 
wind itself, the results are varied, and the periods of submersion and 
_ recession rendered longer or shorter. Sometimes the water will re- 
‘act against the wind; sometimes it will ‘continue to rise, when the 
wind itself has apparently (that is at the spot of observation) died 
away. Sometimes there will be little rise or fall, during the twenly- 
four hours. And it is only during a calm, and that continued long 
enough, and in itself perfect enough, to leave the waters subject o0- 
ly to the operation of these ordinary laws, that an apparently level 
and equable surface is preserved in the lake. 
But it is these variations in the time, the height of water, and the 
number of the changes in any given time, that (without any reference 
to atmospheric phenomena) afford, to my mind, the most conclusive 
evidence that the changes in the diurnal or periodical level of the 
water, are separate and distinct, in their causes, from lunar tides. 
The appearances of a tide rising against the wind, noticed by Capt. 
Dearborn at. the head of the military mill-race at the- Sault St 
Marie, admit of explanation on the principle of a reaction of the 
body of water, confined in that portion of the strait (about ten miles) 
situated between the head of the race (which is also the head of the 
falls) and lake Superior. 
Very respectfully, your obedient servant, 
Henry R. ScHooeraFt 
Before these desultory remarks are closed, it may not be pd 
propriate to notice what General Dearborn terms “ the periodical gt 
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