The evening Argus. [volume] (Rock Island, Ill.) 1861-1871, 1867-02-16


III can do anything more than have done in
forwarding the interests of navigation on the Mis-
sissippi, I hope You win advise me at once and
viii gladly respond -" 80 -s=*'
Very respectfully yours, &C.,
Capt Jas r GriHith. So = : - =.
Below we repeat the last clause of this
letter:
''If can do anything more than l have
done in forwarding the interests ofnavigation
on the Mississippi, | hope you will advise me
at once and will gladly respond
Gentlemen, that Is the sentiment of the
engineer corps that have had charge of the
photographic Department of the survey of
the upper rapids of the Mississippi river,and
if the people of the states along that river
were half as earnest in the work as the en-
gineer corps, it would be done Just as soon
as time would let it be done. Applause. !
You have asked for information: have 70
pick it up by piecemeal. will say but very
little about the lower rapids as I am not so
familiar with them, but l will briefly call
your attention to one phenomena At the
lower rapids we have river FIVE thousand
feet wide. At the lower rapids we have a
river the area of whose cross section is but
very little more than the area of the cross
section of the river at the upper rapids.
Hence, you have no more water spread
over FIVE thousand feet at the lower rapids
than you have spread over less than two thou
sand feet at the upper rapids. So YOU see at
once the phenomena of the rapids is entirely
different. The lower rapids is one continu-
Gus chain of rocks. The water is spread
over them at an average of three four and
five feet, perhaps in pools not exceeding a
depth OF five or six feet at the most, the up-
per rapids being succession of deep pools
very deep In..ar ef .i,e-, nsv~..- ~la-hse
to find bottom with a sounding line 30 feet
long. and obstructed with few chaines which
l will name when | come to examine the
upper rapids.
Now, in the engineering details of the
survey of these rapids. it was determined
early determined-to he impracticable to i'm
prove the natural channel of the lower rapids.
When say impracticable, do not mean to
that money would not accomplish it but that
it would cost so much more, and be so much
less effective than any other class of improve
ments, that the examination in that respect
was modified and made more thorough in
view of the construction of q canal around
the lower falls.
Now, as to the details of that canal. The
canal around the lower rapids will be seven
miles and six-tenths long. The width on the
water line three hundred feet; the maximum
depth SIX and the minimum five feet The
slopes Will be one and a half feet in one foot
The length of the locks will be three hun
dred and fifty feet between the mitre cells.
and the width of the locks eighty feet The
hit OF the upper lock, situated about Nash
vile, will be eighty feet. The lift of the
lower lock, located about eight hundred feet
above what is called Pilots Indicator, at Keo-
kuk, VIII bs~ten feet and three tenths. The
area OF the cross section of the canal will
equal 400 feet maximum. The surface vel
ocity that Will be admitted in the canal will
De equal to one mile per hour. The volume
OF discharge will be equal to 103,l62 cubic
feet per minute. The water power, or theor-
encal power, will be equal to 1925 horse
power The efiectual power win equal 1,356
horse. Now, inasmuch as this estimate of
water power is predicated upon the idea that
there Is no navigation passing through the
canal-no exhaustion of water by loekages,
It Is no more than lust to estimate at what
extent the lockage will naturally destroy
hat water power. And it is estimated that
/ lockage of TWENTY-FIVE boats per hour will
,reate the maximum current allowed within
he canal
In constructing or improving the lower
apids, from Nashville north from a certain
distance, it is necessary from an amount Of
excavation at the head of the lock to get five
eet in depth. That lock lifts down eight
eet into the canal below. That is construct
ID by building the marine wall outside of the
bank Of the river, and being seven and six.
enths miles in length 1T is long enou Oh be-
oweal the distractions of the rapids an To-
ate 1t In the water the necessary DEPTH
All the surveys of the lower rapids, as we'll
Is the upper rapids, are reduced to the plane.
# reference called low water stage. equal to
1914.
As to the examination of the upper rapids,
{ time and opportunity offered, 1 could speak
o you more fully, as / had charge of the
he photographic department of that survey.
made great number of soundings, not less
han 5000, last fall. made thorough rec
'gnizance of those rapids, and we early de-
that it would be best to improve
he natural channel there not that there are
10 arguments against canals at all, other
han the single exception of the principle of
1t is well known that we will have
reat trouble to get money for improvements.
We see by the morning papers that they have
lven two hundred thousand dollars for the
Improvement of the upper rapids and one
aiilon for the lower, yet the engineering
Kill shows that the upper rapids can be i'm.
roved III twelve months, and tb ey give us
wo hundred thousand dollars to Improve
hem in twelve months, when we SIX for three
uarters of million. -
AT the upper rapids, commence, ~ at point
eia .s the railroad bridge, the ave rage depth
the water in the channel is Fl. orn nine to