LEVEES OF THE MISSISSIPPI. 511 
and the interests which might be sacrificed by a change of 
system are too vast to be hazarded by what, in the present state 
ot our knowledge, can be only considered as a doubtful exper- 
iment.* 
The embankments of the Po, though they are of vast extent 
and have employed centuries in their construction, are inferior 
in magnitude to the dikes or levées of the Mississippi, which are 
the work of scarcely a hundred years, and of a comparatively 
sparse population. On the right or western bank of the river, 
the levée extends, with only occasional interruptions from high 
bluffs and the mouths of rivers, for a distance of more than 
elevenhundred miles. The left bank is, in general, higher than 
the right, and upon that side a continuous embankment is not 
needed; but the total length of the dikes of the Mississippi, 
including those of the lower course of its tributaries and of its 
bayous or natural emissaries, is not less than 2,500 miles. They 
constitute, therefore, not only one of the greatest material 
achievements of the American people, but one of the most 
remarkable systems of physical improvement which has been 
anywhere accomplished in modern times. 
Those who condemn the system of longitudinal embankments 
have often advised that, in cases where that system cannot 
be abandoned without involving too great a sacrifice of exist- 
ing interests, the elevation of the dikes should be much re- 
duced, so as to present no obstruction to the lateral spread of 
extraordinary floods, and that they should be provided with 
sluices to admit the water without violence whenever they are 
likely to be overflowed. Where dikes haye not been erected, or 
where they have been reduced in height, it is proposed to con- 
struct, at convenient intervals, transverse embankments of mod- 
* Dupenchel advised a resort to the ‘‘ heroic remedy”’ of sacrificing, or con- 
yerting into cellars, the lower storeys of houses in cities exposed to river inun- 
dation, filling up the streets, and admitting the water of floods freely over the 
adjacent country, and thus allowing it to raise the level of the soil to that of the 
highest inundations.—Traité @ Hydraulique et de Géologie Agricoles. Paris, 
1868, p. 241. 
