The Charleston daily news. [volume] (Charleston, S.C.) 1865-1873, 1870-01-13
Il MIGHTY WORK.
The Process of Bridging the Mississippi
Mt st. Louis-Hoyv the Piers are Built
A Triumph of Science.

fhe Process of Bridging the Mississippi
ut St. Louis-How the Piers are Built
A Triumph of Science.
A reporter of the 81. Louis Democrat gives
the following graphic description Of how Colo
mel Eads is sinking the great iron caissons for
the piers to the bridge across the Mississippi at
that city:
Two immense piers are to be constructed in
the river of solid stone masonry. These piers,
to be substantial, must rest on the sold rock
that lies fifty, sixty OF q hundred feet under
the sand. under the water OF the rushing river.
The question was how 10 get down all these
feet through water ana sand, to find the rock
10 lay the solid foundation. One way would
have been to build Golfer dams, and pump out
the water, dir out the sand, and lay the piers
in the empty space But this was impractical
lie. if not impossible, and Mr.. Eads' science
and wisdom selected another plan, which,
though not original with him, mas oeen sI sreatiy @
improved on by him, anthapplied more scnsl-
bly, and effectively than it was ever done be-
fore. This plan was to build within caisson
till the rock was reached and the pier COM
pleted, and to make this comprehensive to
every child it shall be Illustrated very simply
ILLUSTRATIONS OF THE SINKING cAIssoN.
Did you ever hold goblet bottom side up,
and press it down into vessel OF wafer f! ii
YOU have YOU know the water does not enter
into the empty tumbler, but the air in 1t keeps
the water out, and as you sink 1t and press it
down it drives the water up the sides Of the
vessel Now suppose instead OF the goblet you
hold an inverted metallic vessel IN the same
way, the same facts would be true as long as
the air was inside of it. If the bottom of this
inverted vessel were fiat, you could put brick
on it, and another, and another, until you have
weighed enough to sink it to the bottom OF the
water, when you have pier OF bricks. Now
this is exactly what Colonel Eads has done in
building the eastern pier Of the bridge. But
his inverted 'pan" is of the size he wishes the
bottom of the pier to be- and Is 40, SO or GO feet
across, as the case may be. or course this
immense "iron DISH" bottom side up, was
held in position on the water by machinery.
He then laid solid courses of stone masonry
on the ''dsh" or "caisson," and as he built the
weight pressed 1t down into the river, and now
1t has reached the bottom of the river, and
even six feet into the sand, and the pier Is for
ty or fifty feet high. But 1t has yet to sink
fifty or sixty feet further to meet solid rock,
and the sand cannot be displaced as the water
was, but must be removed by artlflclai means,
and this is what is being successfully done
now. OF course, as the sand is dug away
from under the sides of the casson it will
sink just as fast. To dig this away men must
get into the ''up-turned dish" or "caisson," or
Hair-chamber' under the pier and work there.
we Will explain IOW liliS ID uouc.
ENTERING THE AIR CHAMBER.
Every one will understand that the air in the
chamber must be very much condensed, and
that most essential requisite is that it must be
kept So and not allowed to escape. Ii direct
opening were made to 1t anywhere, the escape
Of air would cause the water and sand to wash
in from underneath, the vacuum would be In
stantly filled, and there would be the end OF
sinking the caisson and the pier. Colonel
L. INN a n n
way of entering this chamber, which is now
six or eight feet lower than the bottom OF the
river, and yesterday we went down into
1t and saw the men at work. In the centre OF
the pier he left circular well, nicely
finished with brick sides, and six or
the very bottom, is now fifty feet deep,
and has flight of steps built cir
cling, next to the wall, from top to bottom.
Down these steps we went together to the
bottom of the well. There we found door OF
an oval shape, and about two feet in diameter
Looking in we saw a room about six feet high,
deep and wide-a sort of cold and damp
t'oyen.n "Crawl in and I'll follow" said Colo
mel Eads In we went through the oval hole,
knocking off hat, and slightly humping
head. Colonel Eads came also, with pine
stick and IL lighted candle stuck on it, or we
colonel closed the little iron door by which we
had entered, and it shat us in 'air tight He
then pointed to another similar door right op-
posite, and said: ''That opens directly into the
air-chamber under the whole pier. Twill let
the compressed air in here gradually, and
when the equilibrium is established, that door
will open Of itself, and we will 20 in through
brass stop-cock, the air from the
air-chamber came singing through it like
steam from boiler valve. The strange SEN
sation crept over us: What tifsomething should
o YI,of onr,lI
the door behind us, now being held by the
giant pressure of the compressed air Sup
pose tainting came over one, and this roaring,
ringing, laundering in the ears should lust for
life But in just one minute and half the
rush of air ceased, the door opened, the ears
were all right, and with no unpleasant sensa-
ton we were in the condensed atmosphere,
the sand into the airchamber. Ten or dozen
men were hard at work. each with candle,
the huge caisSon was all around US, glsteninS |
with water-drops and from rust in solution,
and the fiat, iron roof was overhead. with all
its tons of stone and pier above us. The sand
was damp, but not wet, as the compressed at
mosphere drove all the water out through the
sand and mp through the water, which we had
observed before we came down, to be bub- |
bling all around the pier, like champagne in q
glass.
WHAT WE FOUND UNDER THE PIER.
We walked all about the air chamber from
end to end, and side to side, and saw how the
sand is removed, and how the dir is supplied
for the inmates to live on. Powerful uir
pumps, worked by steam on boats upon the |
surface of the river, force water down tubes
that are run through the stone work OF the |
pier, and they keep the atmosphere pure. No |
less than seven powerful sand pumps are also |
seen with their feet projecting down to the bot
tom and lifting it up through the pipes, and |
throwing it out above the river Three OF |
these pumps will take this sand away as fast as |
workmen can lay the stone work on the pier,
and in four hours the pump we saw at work
took out 81 cubic feet in IL minutes, or one
hundred carloads in about four hours. But
how can pump throw out sand some one
asks. just rs silly as we were before we saw
it, temporary well, or box, is put under the
foot of a p1mp, and large hose brings down
water from Il force pump above. The hose |
opens in the box, the water is sucked up the |
sand pump, anu TWO or three men shovel sand |
into the box TO mingle with the water and be
thrown out with it-and that is how the sand |
pumps work ! Their SUCCESS has been fully
tested-the work is going on satisfactorily
and if good luck happens, Colonel Eads will
find his first great pier resting on the solid
rock within thirty days from now
INGUL1R PHENOIENa.