Nashville union and American. [volume] (Nashville, Tenn.) 1868-1875, 1870-01-19
A MIGHTY WORK.

The Process OI Bridging the Mis-
sissIppi at ~. LOUis-EOW the
Piers are BuiIt-A Triumph of
science.
A reporter of the St Louis Democrat
gives the following graphic description OF
how Col. Eads is sinking the great iron
caissuns for the piers to the bridge across
the Mississippi at that city:
Twoimmcnsc piers are to be constructed
in the river Of solid masonry. These
piers. to be substantial, must rest on the
solid rock that lies fifty, sixty OF hundred
feet under the sand, under the water OF
The rushing river. The question was how
10 get dogn all these feet through water
and sand, to find the rock to lay the solid
foundation. One way would have been
10 build Golfer dams, and pump out the
wafer, dig out 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 original with him, has
been greatly improved on by him, and
aDplied more sensibly and effectively than
il was ever done before. This plan was
20 build within a caissOn till the rock was
reached and the pier completed, and
% make this comprehensive to every
.LHd il shall be illustrated very SIMPLY.
ILLUSTRATIONS OF TIE SINKING CAIssoN.
Did YOU ever hold goblet bottom side
IN and press it down into vessel OF
water If you have you know the water
hoes not enter into the empty tumbler,
! mt the air in it keeps the water out, and
4 3 YOU sink it and press it down, 1t drives
ne water up the sides Of the vessel Now,
,nDosc instead of the goblet you hold an
,tdrtcd metallic vessel in the same way,
40 same facts would be true as long Gs
no air was inside of it. If the bottom OF
ia inverted vessel were flat, you could
M; q brick on it, and another, and anoth-
!. until YOU have weighed enough TO SINK
IN the bottom of the water, when you
,,~e a pier OF bricks. Now this Is exact
vbat Col. Eads has done Including the
orn pier of the bridge. But his IN.
ed ..pan" is Of the size he wishes the
n,tom of the pier to be, and is forty,
,t,- or sixty feet across, as the case may
or roursc this immense Iron dish,
,,,om side up, was held in position OF
40 wafer hy machinery. He then lalC
in courses of stone masonry on th'
Tsb~ or 'caisson,n and as he built The
-si-bt messed it down into the river, anC
NV if has reached the bottom of The
: ve-. and even six feet into the sand, AM
ne pier is forty or fifty feet high. But l
,as vet to sink fifty or sixty feet furthe
meet solid rock, and The sand cannot b
isnlaccd as the water was, but must b
rmoycd by artificial means, aud this !
.har i. being successfully done now. O
nurse. As the sand is dug away from IN
.cr the sides Of the caisson it viii sin
ms, AS fast To dig this away men mus
rrt into the ''up-twned dish or ''cais
an. -" or "air-chamher under the pier an
york there. We viii explain how this
lone.
ENTERING TIE AIR CHAMBER.
Every one will understand that the a
~ the chamber must he very much cor
.I.r-,l. and the most essential rcQuisii
-. thai II must De kept so, and not above
% escape. Fl. ID direct opening were mao
70 il anywhere the escape OF air wou!
,arsr the water and sand to wash in fro
,.r5e~ucath. the vacuum would he insian
allied, and there would be the end
apkfng the ca'ss'n and the pier Co