Great North American Lakes. 85 
of Michilimackinac, and mentions the fact, that in passing 
that strait, his canoe was carried with the current against a 
head wind.” In another place, in speaking of an apparent 
flux and reflux of the lakes, he supposes that it was “ owin 
to the springs at the bottom of the lakes, and to the shoc 
of their currents, with those of the rivers, which fall into 
them from all sides, and thus produce, those intermitting 
motions.”’* 
‘From all these circumstances there is reason to conclude, 
that a well conducted series of experiments, will prove, that 
there are no regular tides in the lakes, at least, that they do 
not ebb and flow twice in twenty-four hours, like those of 
the ocean—the oscillating motion of the waters is not attrib- 
utable to planetary attraction—that it is very variable as to 
the periods of its flux and reflux, depending upon the levels 
of the several lakes, their length, depth, direction, and con- 
formation—upon the prevalent winds and temperatures, and 
upon other extraneous causes, whic i measure 
* Charlevoix’s Journal, Vol. 1. p. 314. 
