216 On the Tides in the great North American Lakes. 
just before the rise in 1828, and have marked the continued eleva- 
tion since that time, until the recent subsidence. There is not the 
same certainty as it respects the elevation of 1800; but there is no 
reason to doubt the concurring testimony of two or three respectable 
affirmers to the fact. The condition of the road—a great thorough- 
fare—alluded to, is a familiar and striking criterion, and likely to 
make an impression. ‘There is no tradition, that we know, reaching 
farther back, excepting what may be inferred from the general belief 
of the old settlers, that the rise and fall is periodical as before stated. 
- As far as these facts go, they certainly favor the popular theory. 
but it rests on these facts alone. In every other point of view, 
it is improbable and seemingly absurd. ‘There does not appear 
to have been any observations made on the character of the sea- 
sons immediately preceding and accompanying the elevation of the 
waters. We are therefore in the dark as to such causes as copious 
rains abundant snows. 
. Abrupt and very considerable changes in the level of the Detroit 
river are frequently observed. Within twelve hours there will some- 
times be a difference of two or three feet. But this may be satisfac- 
torily accounted for. The Detroit river forms something like the are 
of a circle, the two ends resting on Lake St. Clair and Lake Erie, 
whose courses continue the curve. A strong west or south-west 
wind drives back the waters of Lake St. Clair, thus diminishing the 
usual supply discharged into the river, and drives forward the waters 
of Lake Erie, thus lessening the volume and accelerating the current 
at the mouth of the river. On the contrary, an easterly wind, driv- 
ing down from Lake St. Clair an increased volume of water; and 
heaping it up equally at the outlet in Lake Erie, causes an unusw 
elevation. 
The sudden depression of the waters this winter, (1830-31,) be- 
fore alluded to, is fresh in the recollection of every one, and if any 
obvious causes had preceded it, many would doubtless have observed 
them. It was observed that a strong westerly wind prevailed not 
long before. This would account for a temporary depression, upon 
the principles already explained, but for a temporary one only, a5». 
even if Lake Erie were depressed many feet below its usual level, 
it is evident that the Detroit river would maintain its habitual height, 
provided the supply above continued the same ; and, in the pr = 
instance, that supply would of course return, the moment the wesier” 
ly wind subsided, or the refluent tendency of the accumulated Wa 
ters of the lake should overcome the resistance of that wind. 
