364 Vibrating Dams. 
itself or its cause. Some weeks afterwards, I visited the locality, 
and although the water was at too low a stage to exhibit the phe- 
nomenon in question, I succeeded in obtaining a pretty good de- 
scription of the facts and formed my opinion as to its cause. I 
published a notice of it in the Ohio Observer which led to some 
discussion, and brought to light several similar cases elsewhere. 
As I have not succeeded in finding any notice of this subject in 
such books as I have had the opportunity of consulting, I have 
thought it desirable that the facts should be placed on record. 
I propose therefore to communicate such information as I have 
been able to collect, and shall conclude with some speculations 
as to the cause of the phenomena. 
I. Dam at Cuyahoga Falls, Ohio. 
This dam is a portion of an arc of a circle, the convexity of 
course being turned upstream. It is formed of hewn oak timbers 
one foot square, piled upon each other in tiers, all morticed firmly 
together, so as to form as it were one huge plank two feet thick ; 
twelve and a half feet in breadth, and ninety feet in length, meas- 
ured not between the banks, but between the points of support. 
Its curvature is described with a radius of a hundred and twenty 
feet ; that is, the arc is about one eighth of the circumference of 
acircle. ‘There is an embankment of earth upon the upper side, 
which until recently was left in an unfinished state. The bank 
did not rise to the top of the dam, and sloped off very abruptly. 
This dam was erected in the summer of 1840. During the winter 
of 1840-1 there was noticed considerable rattling of the windows 
of the neighboring houses; a phenomenon different from what had 
ever been noticed before; but during the winter of 1841-2, which 
Was a very open and wet winter, the vibrations were more re- 
markable and became a matter of general complaint. The doors 
and windows of most of the houses in the village would shake 
for days together violently as with the ague, and to such a de- 
gree as seriously to disturb sleep. 'This phenomenon was appa- 
rently somewhat capricious. After continuing for a time, perhaps 
an hour or a day or longer, the vibrations would suddenly cease, 
and after some interruption might be as suddenly resumed. The 
rattling of vibrating objects would frequently cease, while the vi- 
brations could still be felé. A window, when apparently at rest, 
if put in motion by the hand, would continue to rattle. ‘The 
