The Columbia herald. [volume] (Columbia, Tenn.) 1850-1873, 1870-01-14

to employ the committees for long
time. 7
Rules for the regulation of the Con-
vention were adopted substantially
the same as those which govern SINH
lar bodies.
The clergy of the city were invited
to be present and act as chaplains of
the Convention.
In THE DEPTHS.
How Col. Eads Is Bridging the Mis-.
sissippi at st. Louisa Triumph OF
Science.
A reporter of the st. Louis Demo.
crat gives the following graphic descrip-
ton of how Col. 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 con-
structed ia the river, of solid stone ma
sonry. These piers, to be substantial,
must rest on the solid rock that lies
fifty, sixty or hundred feet nnder the
water OF the rushing river. The ques-
ton was how to get down all these feet
through water and sand, to find the
solid rock to lay the foundation. One
way would have been to have built
Golfer DAMS and pump out the water,
dig olt the sand, and lay the piers in
the empty space. But this was imprac-
ticable, if not impossible, and ..Mr.
Eads' science and wisdom selected
another plan, which, though not orig
inal with him, has been greatly i'm
proved on by him, and applied more
sensibly and effectively than it ever
has been before. Thi, plan was to
build within caisson till the rock was
reached and the pier completed, and to
make this comprehensive to every
child, it shall be illustrated very sim.
ply.
ILLUSTRATION OF THE SINKING
CAISSoN.
Did you ever hold a goblet bottom
upward, and press it down into YES
sci of water? If you have, you know
that the water will not enter the tum-
bier, but the air in it keeps the water
out, and as you press it and sink 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 remains on the inside of it. If the
b tom of this inverted vessel were fiat,
you could put brick in it, and anOth-
er, and another, until You have weigh
ed enough to sink it to the bottom of
the water, when you have q pier of
bricks. Now this is exactly what Col.
Eads has done in building the eastern
pier of the bridge. But his inverted
"pan" is of the size he wishes the bot
tom of the pier to be, and is forty, fif-
ty, sixty or q hundred feet across, as
the ease may be. Of course, this i'm
mense - iron dish," bottom side up,
was held in position on the water by
machinery. He then laid solid courses
of stone masonry on the "dish" or
caissOn," and as he built, the weight
pressed it down into the water, and
now it has reached the bottom of the
river, aud even six feet into the sand,
and the pier is forty or fifty feet high.
But it has yet to sink forty or sixty
feet further to meet solid rock, and the
sand cannot be displaced as the water
was, but must be removed by artificial
means, and that is what is being sue
cessfully done now, OF course, as the
sand is dug away from under the sides
of the caisson it will sink just as fast.
To dig this away, men must get into the
"upturned dish,n or "caisson," or
" afr chamber under the pier, and
work there. We will explain how this
is done.
ENTERING THE AIR CHAMBER.
Everyone will understand that the
air in the chamber must be very much |
condensed, and that the most essential |
requisite is, that it must be kept so, and |
not allowed to escape. If direct OPEN
ing were made to it anywhere, the es-
cape of air would allow the water and |
sand to wash in from underneath, the |
vacuum would be instantly filled, and
there would be the end of sinking the
caisson and the pier. Col. Eads has ar
ranged a very simple and safe way of |
entering this chamber which is now six
or eight feet below the bottom of the
river, and yesterday we went down in
to it and saw the men at work. In the
center of the pier he left a circular well
nicely finished with brick sides, and
six or eight feet across.
This well reaches to the very bottom,
is now fifty feet deep, and has flight
of steps built circling, next to the wall,
from bottom to top. Down these steps
we went together to the bottom of the
we'll. There we found adoor of an oval
shape, and about two feet in diameter.
Looking in we saw room about six
feet high, deep and wide-a sort of cold
and damp" oven.' Crawl in and I'll
follow,n said Colonel Eads. In we
went through the oval hole, knocking
off hat, and slightly humping head.
Colonel Eads came also, with pine
stick and a lighted candle stuck on it, or
we should have been in Egyptian dark
ness. The Colonel closed the little iron
door by which we had entered, and it
shut US in .ssair-tight." He then pointed
to another similar door right opposite,
and said: /" That opens directly into the
under the pier. Twill let
the compressed air in here gradually,
and when the equilibrium is establish
ed, will go in through it." So saying he
turned the faucet of q brass stop-cOck,
the air from the air-chamber came sing
ing through it like steam from boiler
valve, the strangest sensation crept over
US. 80 - l.f ga,q,.
What if sonething should burst down
here? What power could open the door
behind us, now being Held by the giant
pressure of the compressed air? Sup
pose fainting came over one, and this
roaring, ringing, laundering in the ears
should last for life! But in just one
minute and a half the rush of air ceased,
the other door opened, the ears were all
right, and we were in condensed atmOs>
phere, and crawling through the door,
stepped upon the sand into the air.
Ten or dozen men were
hard at work, each with a candle and
huge caisson was all around us, glisten-
ing with water drops, and from rust in
and the fat, iron rOofwas over
head, with all its tons of stone and pier
above us. The sand was damp, but not
wet, as the compressed atmosphere
drove all the water out through the sand
and up through the water, which We
had observed before We came down, to
be bubbling all around the pier, like
in glass.
WHAT WE FOUND UNDER THE PIER.
We walked all about the air G. amber
from end to end, and side to side, and
saw how the sand isremOved, and how