28 CLINTON ON THE GREAT LAKES. 
full moons, and Jeast at the quarters. The minimum of rise within the 
period during which the observations were made, was as much as eight 
inches. ‘The maximum of rise within the same period, was as much as forty: 
inches. Mr. Lecuyer, a gentleman equally intelligent, expressed the same 
opinion as to a tide at Green Bay. 
If these exhibitions of a flux and reflux of the Lakes were only occa- 
sional and incidental, not uniform, and periodical, there would be perhaps 
no great difficulty in assigning satisfactory causes. The Seiches of the Lake 
of Geneva have been ascribed by Mr. Bertrand to the influence of electri- 
cal clouds which attract and raise the waters of the Lake, and he supposes 
that this water afterwards falling, produces those undulations of which the 
effect, like that of the tides, is most sensibly felt where the shores are most 
approximated. 
A more probable cause may be the unequal pressure of the atmosphere on 
the waters, which will of course rise higher as the weight of the incumbent 
air is less, and fallas it becomes greater; and these changes being almost 
always in operation, may account for the almost continual ebb and flow of 
the lakes. 
The cause assigned by Charlevoix is entirely unsatisfactory ; and it is pre- 
mature to form a theory on the subject. Facts and experiments ought to 
precede speculations ; and we must leave it to future inquirers to ascertain 
the facts in extenso—to investigate the causes, and to determine whether 
this phenomenon be owing to the pressure of the atmosphere—the influence 
of the moon—the attraction of the clouds—the convexity or motion of the 
globe, or any other assignable agency. 
2. There is an annual rise and fall of Lake Erie. The rise generally 
commences in March, and terminates about the middle of July; and this is 
* the case sooner or later with the other Lakes. It is owing to the great 
accession of water produced by the melting of snow and ice, and by the 
vernal rains ; and the fall is occasioned by the failure of most of these sour- 
ces of supply in summer. 
8. There is, besides the annual rise of the Lakes, a more extended peri- 
odical one, at least every three years, and then a correspondent declension. 
