One who had resided upon the shores of Lake Superior for several summers says, "Our attention has been directed to the fluctuations in the level of its waters, and while we have failed to detect any ebb and flow corresponding with the tidal action, we have on the other hand noticed certain extraordinary swells, which appear to be independent of the action of the sun and moon." The Jesuit Fathers in 1670-1, had their attention called to these extraordinary swells. In their "Relations," they say, "We found at one time the motion of the waters to be regular and at others extremely fluctuating. We have noticed however, that at full moon and new moon, the tides change once a day for eight or ten days, while during the remainder of the time there is hardly any change perceptible. The currents set almost invariably in one direction, namely toward Lake Michigan, and they almost invariably set against the wind, sometimes with great force." Mackenzie who wrote in 1789, relates a very curious phenomenon, which occurred at Grand Portage, on Lake Superior, and for which no obvious cause could be assigned. He says, "the water withdrew, leaving the ground dry, which had never before been visible, the fall being equal to four perpendicular feet, and rushing back with great velocity above the common mark. It continued thus rising and falling for several hours, gradually increasing until it stopped at its usual height." Professor Mather, who observed the barometer at Copper Harbor during the prevalence of one of these fluctuations, remarks, "As a general thing, fluctuations in the barometer accompanied the fluctuations in the level of the water, but sometimes the water level varied rapidly in the harbor, while no such variations occurred in the barometer at the place of observation. The variations in the level of the water may be caused by varied barometric pressure of the air on the water, either at the place of observation or at some distant points. A local increased pressure of the atmosphere at the place of observation would lower the water level, where there is a wide expanse of water; or a diminished pressure, under the same circumstances, would cause the water to rise above its usual level."