L. Nickerson on the Periodic action of Water. 153 
2 
or the pool is simply a continuation of the stream, and if = 
becomes equial to =, or the height due to velocity becomes equal 
to one-half the depth, both of the original stream, then a-a,=%, 
acase which we shall examine more hereafter. We know that 
through walls of partly quiescent water, not only that of the 
ead angles, but also of superi itio 
D'Aubinson, “ moreover, the water of flowage seem. only to 
eser have observed, at a distance of 3884 feet from the dam, 
98 the velocity of the surface was nearly insensible, whilst that 
at the bo of ” 
Sure, some of the slower water must be dragged along in the 
_ Course of the faster, in quantity and force varying as the differ- 
ence of lateral pressure. We must remember that as in the end 
Teceived from the upper end, i.e., the water of the current, there 
7st then, be a parodia lull until the deficiency caused by this 
ryt h reese he velocity may become less 
ght readily appear that, as the velocity May ve" 
from the hicsbe of sh. stream to the Baiaide this might occur 
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