Physics and Hydraulics of the Mississippi River. 183 
one hand, the investigations of the Chevalier Elia Lombardini 
have shown the supposed facts advanced by the latter class to be 
entirely erroneous, and their apprehensions to be unfounded. 
The effects of cut-offs were likewise the subjects of contro- 
versy among engineers, a controversy which the measurements 
of the Delta Survey must set at rest, since they demonstrate that 
cut-offs raise the floods below them, a conclusion sustained by the 
well-established effects of such works upon dige. 
utlets were advocated by some engineers because they were 
considered a ready and inexpensive means of reducing the 
- On the contrary, they were objected to by others be- 
Callse, as they claimed, outlets would raise the bed and floods of 
the river. The investigations of the Delta Survey prove that 
outlets, in the few localities where they are practicable, may be 
made to reduce the floods to any desired extent in certain divis- 
1ons of the river ; but that they would not be inexpensive, and 
fall, and discharge of the river throughout the alluvial region ; 
the manner ie ehhh the flood is propagated ; the modifications 
in 
drainage of its basin and that of its tributaries; the proportion 
- drainage to downfall; and the discharge of outlets: in fact, 
us tvery important fact connected with the various physi- 
cal conditions of a river and the laws uniting them being ascer- 
sol vite great problem of protection against inundation was 
At the mouths of the river, a similar course has resulted in 
= development of the law under which the bars are governed, 
depth upon them maintained, and the regular advance into 
weg continued; and, as a consequence, the principles upon 
based plans for deepening the channels over them should be 
sy and the best mode of applying them. The rate at which 
the Tiver progresses into the gulf, and the extent, thickness, and 
relative level of the alluvial formation having been ascertained, 
"S Probable age has been estimated; and the ancient form of 
