i.e., less perimeter in proportion to area of cross section.
The ultimate effect of levees and revetments confining
the floods and bringing all the stages of the river into
register is to deepen the channel and let down the slope.
The first effect of the levees is to raise the surface;
but this, by inducing greater velocity of flow, inevitably
causes an enlargement of section, and if this enlargement
is prevented from being made at the expense of the banks,
the bottom must give way and the form of the waterway
be so improved as to admit this flow with less rise.
The actual experience with levees upon the Mississippi River,
with no attempt to hold the banks, has been favorable,
and no one can doubt, upon the evidence furnished in the reports
of the commission, that if the earliest levees had been
accompanied by revetment of banks, and made complete,
we should have to-day a river navigable at low water,
and an adjacent country safe from inundation.
Of course it would be illogical to conclude that the constrained river
can ever lower its flood slope so as to make levees unnecessary,
but it is believed that, by this lateral constraint, the river
as a conduit may be so improved in form that even those rare
floods which result from the coincident rising of many tributaries
will find vent without destroying levees of ordinary height.
That the actual capacity of a channel through alluvium depends
upon its service during floods has been often shown, but this
capacity does not include anomalous, but recurrent, floods.
It is hardly worth while to consider the projects for relieving
the Mississippi River floods by creating new outlets,
since these sensational propositions have commended themselves
only to unthinking minds, and have no support among engineers.
Were the river bed cast-iron, a resort to openings for surplus
waters might be a necessity; but as the bottom is yielding,
and the best form of outlet is a single deep channel,
as realizing the least ratio of perimeter to area of cross section,
there could not well be a more unphilosophical method of treatment
than the multiplication of avenues of escape.
In the foregoing statement the attempt has been made to condense
in as limited a space as the importance of the subject would permit,
the general elements of the problem, and the general features
of the proposed method of improvement which has been adopted
by the Mississippi River Commission.
The writer cannot help feeling that it is somewhat presumptuous on
his part to attempt to present the facts relating to an enterprise
which calls for the highest scientific skill; but it is a matter
which interests every citizen of the United States, and is one
of the methods of reconstruction which ought to be approved.
It is a war claim which implies no private gain, and no compensation
except for one of the cases of destruction incident to war,
which may well be repaired by the people of the whole country.
EDWARD ATKINSON.
Boston: April 14, 1882.
APPENDIX C
RECEPTION OF CAPTAIN BASIL HALL’S BOOK IN THE UNITED STATES
HAVING now arrived nearly at the end of our travels,
I am induced, ere I conclude, again to mention what I consider
as one of the most remarkable traits in the national character
of the Americans; namely, their exquisite sensitiveness and
soreness respecting everything said or written concerning them.
Of this, perhaps, the most remarkable example I can give is
the effect produced on nearly every class of readers by the
appearance of Captain Basil Hall’s ‘Travels in North America.’
In fact, it was a sort of moral earthquake, and the vibration it
occasioned through the nerves of the republic, from one corner
of the Union to the other, was by no means over when I left
the country in July 1831, a couple of years after the shock.
I was in Cincinnati when these volumes came out, but it
was not till July 1830, that I procured a copy of them.
One bookseller to whom I applied told me that he had had a few
copies before he understood the nature of the work, but that,
after becoming acquainted with it, nothing should induce