Grant County herald. [volume] (Lancaster, Wis.) 1850-1968, 1875-12-30

A Wall Forty Feet High to Hold Up
the Mississippi River.

Minneapolis Correspondence N. Y Graphic.
send you herewith plan for the
gigantic work now being prosecuted
by the Federal Government al this
point TO preserve the Falls of St.
Anthony and the vast water-power
from destruction, and, as final end,
to maintain the 600 miles of steam
boat navigation in the Mississippi
river above this city. 1t is one of
the largest, most necessary, aud pro-
fitabe pieces of internal improve
ment now being prosecuted within
the limits of the United States. -
The river at this point, after flow
ing serenely for 600 miles, suddenly
drops over a limestone ledge and
falls fifty feet in one lunge, creating
the largest available water-power in
the world. Since Father Hennepin
named the fall, 200 years since, it has
receded nearly half mile up the
river, and the water-marks along the
bank prove that the fall at one time
was at Fort Snelling, eight miles be-
low. This constant retreating OF the
fall is caused by the breaking away
and dropping down of the limestone
stratum, as it is undermined by the
backseC at the foot of the cataract.
The limestone ledge is only from nine
to fifteen feet thick, and "runs OUT
10 bed of sand a quarter of mile
above the brink of the fall If this
obstruction to the channel should get
under it, the water-power here and
the hundred of miles of navigation in
the river above would be forever des-
troyed To prevent these calamities
is the object of the pending improve
ments.
The peril of the falls was greatly
increased seven years ago by fool
ish project Of the Tunnel Manufacture
turing Company, which excavated in
the sandstone, under the limestone,
tunnel the whole length of the
Hennepin Island, its purpose being to
serve as tall race under the sites of
manufactures to be built. Water
was to be received above the fall and
discharged below it. The precious
work had proceeded to the foot of
Nicolet Island, when, in October,
1869, the tunnel was invaded by the
waters of the Mississippi river. The
original tunnel was 6 by & feet, but
the rushing waters soon excavated a
sluice-way through the soft sand
rock, 164 feet high and from 10 to 80
feet wide. SO much of the sand rock
speedily washed out that large masses
of superintendent lime rock were
undermined and fell into the tunnel
Rude cotfer-dams were built up to
keep the river in its channel, if
possible, but there were rude breaks
in the limestone, and the destruction
OF tne WnOi0 w.sS4 ~ -. "@s rsri
ously threatened. After the citizens
had taxed themselves heavily the
Federal government came to their
assistance. To prevent the opening
out Of permanent channel under
the falls, solid bulk heads of masonry
were built in the tunnel, and means
were devised to cut off the percola-
ton through the underlying sand
rocks, which is 80 soft that it is
easily cut with knife. At last it
became evident to Col. +. u. FarQuar,
Government Engineer in charge,
that nothing could save navigation
and the water power short of two
tremendous walls of water-tiGht
masonry under the limestone ledge
at both ends to hold up the river.
This great work is now being execu-
ted. The lower wall, or dyke, as be-
ing the most Immediately necessary,
is being built first. Two hundred
men are working in three relays,
night and day, on the immense
structure. The sustaining-wal just
above the fall, is underneath the
limestone lsdge (which rests upon its
top), and extends from one bank of
the river TO the other. 1t is 1850
feet 10 length (more than third Of
miIe,) 40 feet high, and feet thick
It's base is 20 feet below the water
level, and some 20 feet lower than
the foot of the fall. This, it is be-
lieved, will effectually prevent the
breaking through of amy new channel
1t is ssid that the water has never
gone more than II feet into the sand
rock to do any damage. The pecul-
lar silcious formation runs down for
1000 feet, but it is quite firm and
solid below the bottom of the dyke.
The construction of this wall is
now being pushed rapidly by MIR. J.
l.. Gillespie, C. E., in charge. The
cut of the wall. 40 feet high, has been
excavated nearly to the Minneapolis
(west) shore, and the concrete of
cement and crushed stone is more
than half filled in. | was in there
to-day, shielded with rubber and
armed with a torch, as if for jour-
ney in tho Mammoth Cave. And il
is almost as weird and ghostly--a
trip seventy feet beneath the Missis.
sippi. Down in deeper pits and off in
side shafts as in a coal miae, work.
men are swinging picks and shovels
10 dim light, cars on rushing by on
subterranean tramways, pumps
wheeze automatically and buckets go
up and down, drawn by the arm of
the steam giant that shakes Henne-
pin Island far overhead.