E.. Loomis on vibrating Water-falls. 353 
three feet of the edge. Mr. Edwards, who resided near the dam, 
had determined that 
When the height (10 inches, the number 280 per minute. 
of the water 82.2% 9) 300 « 
on the edge a vibrations $35. 
of the dam was Be ** was over 400 « 
I at once perceived that these numbers indicated a general 
law; viz., that the time of one vibration is nearly equal to the time 
in which a heavy body would fall through a space equal to the depth 
of water on the dam. ‘This will appear from the following table, 
in which column first shows the depth of water on the edge of 
the dam; column second shows the time of one vibration ex- 
pressed in fractions of a second; and column third shows the 
time which a heavy body would require to fall through the 
spaces in column first, and is computed by the formula t= 
Column fourth shows the quotients obtained by dividing the 
numbers in column second by those in column third. 
Depth of Time of Time of falling | : 
waler, | a. or Ra throngh depth. Ratio. | 
10 inches. 08°214 0s-228 0940 | 
a. & 0-200 0 +204 0-982 
a 0°179 0 -190 0940 
ee is less than 0 ‘150 0-161 less than 0°932 
In April, 1861, a’portion of this dam, about 70 feet in length, 
was carried away, and was rebuilt during the following summer. 
_ the h 
_ upin front at a slope such that with a depth of 
