352 E. Loomis on vibrating Water-falls. 
In the above way, (as well as in its non-percipient nature,) the 
plant exhibits complete decephalization—a condition to which 
the Radiate only approximates, as it has generally, if not always, 
an anterior and posterior side, besides other animal characteristics. 
Note to page 827.—The term elliptic, as used on page 327, im- 
plies defectiveness or deficiency of paris through abnormal wea 
mess in an organ or the general system. The foot of the horse, 
one of the examples mentioned, is therefore hardly elliptic, since 
it has its full normal strength in the one toe, ae being enlarge 
at the expense of the others. Paragraph a and the second under 
6 hence require correction accordingly. a the fifteenth line 
from the foot of the page, Animal-type should be Mammal-type. 
Art. XXX.—On vibrating Water-falls ; by Et14s Loomis, Pro- 
fessor of Natural Philosophy and Astronomy i in Yale College. 
In the year 1848, I published in this Journal, vol. xlv, p. 360, 
a notice of several water-falls which at times exhibite very 
strong vibratory motion. Iam not aware that any one else had 
ever published anything on this subject previous to that time. 
In that article, I proposed an explanation of these vibrations, 
which was naturally suggested by the only case which I had 
myself had an opportunity to investigate; viz., that the dam. 
itself was the vibrating body, and that the vibrations were 
analogous to those of a stretched cord, The attention of several 
other observers has since been called to the same subject, and 
Prof. Snell has endeavored to show that the vibrating body is 
the column of air behind the sheet of water, and that the time 
of vibration depends upon the length of this column. I have 
thus been led to examine the subject anew, and have been com- 
pelled to modify the views which I first published. I have 
made a large number of observations on several different water- 
falls, and have obtained numerous observations made by other 
persons. These observations have been made chiefly at three 
places, viz: at South Natick, Mass.; at Holyoke, Mass. ; 
at Lawrence, Mass. 
Observations at South Natick, Mass. . 
In August, 1859, Mr. William Edwards communicated to me 
the results of numerous observations weg he had made upon a 
water-fall at South Natick, Mass., about 18 miles west of Bos- 
ton. The dam — which the water fell, once of two sepa- 
cn et One of them, the e northern, was | et long 
| pray ponies Satee built of hewn timbers generally about 10 inches — 
square, gether, and banked: & up with earth to within _ 
