LAKE ONTARIO, 79 
to determine the truth of observations of such 
a nature, have never staid a sufficient length of 
time there to have had it in their power to 
do so. 
A long series of minute observations are 
necessary to determine positively whether the 
waters, of the lake do or do not rise and fall 
periodically. It is well known, for instance, 
that in wet seasons the waters rise much above 
their ordinary level, and that in very dry sea*- 
sons they sink considerably below it; a close 
attention, therefore, ought to be paid to the 
quantity of rain that falls, and to evaporation; 
and it ought to be ascertained in what degree 
the height of the lake is altered thereby ; other¬ 
wise, if the lake happened to be higher or 
lower than usual on the seventh year, it would 
be impossible to say with accuracy whether it 
were owing to the state of the weather, or to 
certain laws of nature that we are yet unac¬ 
quainted with. At the same time great at¬ 
tention ought to be paid to the state of the 
winds, as well in respect to their direction as 
to their velocity, for the height of the waters 
of all the lakes is materially affected thereby. 
At fort Erie, situated at the eastern extre 
mity of the lake of the same name, I once ob¬ 
served the waters to fall full three feet in the 
course of a few hours, upon a sudden change 
of the wind from the westward, in which di- 
