The morning news. [volume] (Savannah, Ga.) 1887-1900, 1891-11-02

49, -" a1r- -sFlf AtHA !. n CH>L iron IuLe
formed Of plates inch thick and riveted
together ON fianges eight inches deep. They
also gave up the work with shovels
and 6 pilot and adopted the Beach
SHIELD for pushing through the slit
This shield was first used to build the ex-
perimental rapid transit tunnel that still
Hes 500 feet under Broadway from Warren
street 20 the present New York postoIIice
That was 10 l569-70. and later it built tun-
nels under tue Thames, and still later the
~ Clair tunnel The shield that no closes
the end Of the completed portion of the Hud-
son river tunnel consists Of cylinder ten
feet long and twenty feet in diameter. or
one foot eight inches larger around than
the iron tunnel itself. A few feet Of its
inner edge always overlsps the plates form
ing the facing of the tunnel, 50 as TO allow
no opportunity for caving in Of the soil
This great shell weighs eighty tons IT'S
driven forward by sixteen hydraulic jacks
placed around its inner edge, and when
pushing braced against the last plates Of the
tunnels facing. Each Jack is capable OF
exerting driving force Of fifty tons.
While the shield was to render possible a
reduction Of the air pressure in the tunnel
below what had been required for safety
under the old system, its Introd uction there
in fragments was lar from having that
effect. To build 1t in its correct position a
chamber much higher and wider than the
tunnel had to be excavated. The soft silt
walls of this chamber were sustained dartly
by timber, but mainly by the resistance OF
compressed air. For several weeks the men
worked in putting this shield together I'M
der a pressure OF forty three pounds. They
also were subjected to an exceedingly high
temperature on account OF the heat from
the rIveting furnaces. which were kept
burning in the tunnel night and day.
1t was during the building Of the shield
when the ambulance lock, as it is known at
the tunnel. came into existence. So many
men had the bends a disease TO which
those working in compressed air are sub
ject, that something had TO be done. Three
men died at the entrance Of the tunnel be-
fore medical aid could be summoned, and
many went to the hospital suffering torture
or complete paralysis. Since that time the
ambulance lock has done good service /;
is in shed adjoiping tue engine house
and Is nothing more than a hollow wrought
iron boiler, 20 feet long and feet in diam
eter, divided into two compartment by an
iron partition. The low doors entering from
the outside and to the second chamber OF the
huge cylinder are OF heavy iron and fit IN
tight by me ms Of a rubber edglug. An
affliction OF the bends is usually the
result of being in too much OF u hurry
in leaving the tunnel. After having been
i'll the compressed air for several hours it i'd
necessary 20 spend some time in the locks
that form the gateways between the differ
ent sections OF the tunnel, where the pres.
sure is less than in the compartment the
man has left, but it's still higher than the
normal atmospheric pressure. Men who
neglect this precautiou are often, on coming
out of the tunnel seized with severe cramps.
In extreme cases they lose all power of mo-
ton or speech. Now when person has the
bends at tho Hudson river tunnel he is
hustled into the fur her compartment of the
ambulance lock. The doors are closed and
a pressure of dir is turned on. If an at
tendant has gone with the sufferers into the
lock he can withdraw after the compressed
air has entered by passing into the outer
compartment and fastening the door behind
him he is then free to leave the lock by the
other door. The contracted joints OF the
victim OF the bends generally
relax soon after the gauge at the
front Of the ambulance lock shows
that there is "a thirty-pound pressure inside
aud then the pressure is gradually reduced
Men have been taken into this big cylinder
as utterly collapsed as if they were dead
and in half an hour after the pumps begaI
forcing air into the leck they were able tt
walk out Of it with all their muscles and
senses restored to their normal activity.
The mules that drew the silt from tn
| shield TO the air locks are stabbed and fe
inside the tunnel. never coming out fror
the compressed air while the work is goinl
| on. Those that worked there recent,
grew fat and thrived, had voracious appe
titles and were exceedingly lively, even foI
mules From the shield the animals drew
the silt to the bulkhead that was put in las
spring. Here a hydraulic elevator raise
the carts no the entrance to the lock. al
| iron door SKA feet. The cart passes through
| and along the tramways to th'
next lock. In the first Ito,
fest of the tunnel, where compressed air i
not used, other mules are stationed, which
are attached TO the carts as t-ey leave thu
last air lock. Recently, when the six mule
which had lived a year or more in the com
pressed air of the tunnel were taken out
they underw went great suffering They wer
carefully doctored, mainly with whisky, TO
some weeks. and when necessary returned
for time to compressed air.
The last lock IN the tunnel is worthy o
description, as 1t is different from any pre-
viousy built In the tunnel under the com
pressed air system. IL consists of tw'
boiler-like cylinders standing side by sid
lengthwise Of the tunnel. They resemble il
appearance the ambulance lock, but are o
heavier iron and with larger doors. wbic
are placed at either end. There IS but on
| compartment in each cyliuder. Or the sid
facing the uncompleted end Of the tunnel
where the air pressure is maintained at
high point, brick wall four feet in thick
ness is built around these cylinders, form
ing an air-tight partition in the tunnel
Ten or twelve feet back of this. near I'll
other end of the cylinders, a two foot par
ttion will be built, and between these tw'
partitions heavy cross walls are cor
structcd forming strong braces to the al
ready powerful partitions
Nearly SO, 900, 900 has already been sDen
on the Hudson river tunnel. Englnee
Hutton estimates that building it as an iro
tube the remainder of the work will cos
$500 foot, aud that by opening new shafts
and prosecuting the work at all availabl
points the north tunnel can be entrel
completed i'll one year. There are go
feet yet to be constructed before the shiel
will enter the shaft that was built eeve
years ago at the foot of Morton street !
New York, but which has been closed 70
many years. Then there remains 4, 900 fee
20 tunnel under Jersey City until the poiu
OF the proposed exit is reached, and 4,50
on the New Yerk side.
The projected terminus Of the tunnel
just below Washington square, where tn
plans are for a grand passenger and freign
depot. which will be the most important /
New York city. Several imaginative brain
have worked out elaborate ideas of th
union depot to include great hotel on til
plan of st. Pancras station in London, bu
the American contingent of tue English
men who own the tunnel at least, are nc
wasting much time over depot plans ult
they are more certain of their money I
complete tue work they have already con
tracted for. The recent and futur
all IL.