L. Nickerson on the Periodic action of Water. 151 
a y . 
Arr. XIX.—Periodic action of Water ; by Louis NicKERSON, 
‘IN reading, some weeks ago, the article by Prof.-Loomis, on 
the vibrations of water flowing over a dam, I was somewhat 
surprised at the idea of deriving the peculiar motion from a for- 
eign source, as a column of air; surprised, because, however 
much the air might effect, by reaction, after the action had com- 
menced, the perturbations of a liquid, in whatever state of mo- 
tion it may exist, have always been so connected with periodic 
action as to have given use to the name of its most common at- 
tribute “the wave,” as the characteristic title ‘of nearly all 
periodic action. Without an attempt to discuss the question 
with the distinguished gentleman engaged, I shall endeavor to 
point out the manner in which the vibrations may be considered 
simply as the result of a: wave peculiarly cireumstanced. _ 
I was sitting one day upon the bank of a large river in the 
est. " Before me was a strong ripple, supposed by the people 
around to have been caused by the lodgment of snags upon the 
bottom. The sound from it was much louder than the roar of 
Wwaten, position was just upon the middle of an are, which 
alate “caving in” of the bank had indented, each point of the 
are running past the average bank of the river toward the 
enter. T e 
oO 
g 
i=] 
wet 
oh 
a 
Jt 
= 
Loe | 
° 
4 
6B 
° 
FR 
aa 
o 
O° 
ct 
° 
Q og 
© 
4 
et 
°o 
= 
rs) 
* 
Qu 
oe 
> 
a) 
==] 
Cnn ae 
& 
= 
Ss 
r= 
Qs 
i=} 
"2 
hat the lower current rr regains its ascende driv- 
a Ns back to be again cl 
ea eee o's 
