The sun. [volume] (New York [N.Y.]) 1833-1916, 1908-03-29

party passed into tube B and started bash
toward Long nland CITY. Soon they cam
upon the shields marking the junction o
the two sections Of this tube. The shari
biting edges Of the two shields rested againg
each other like the blades Of q pair'of nal
clippers. Just behind the shield the rool
and silt showed through, ready 10 be oovereC
with the batteau shaped plates.
These shields are ungainly looking con
trivRnces. Each IL tWenty-three feet eI
and q half inches outside diameter by
eighteen feet long and weighs 3lb tons
TWenty-seven hydraulic jacks, nine inches
IN diameter and with a water pressure
Of 5000 pounds TO the square inch, resi-
against tho hanRe OF the ring last Get and
kick the shield onward with a 5000 ton
pubh.
Through & n materials the shield cute
lie own way without help When II strikes
Fock dynamite has 10 be called ~ When
rock e ahead q rough heading II driven
In advance Of the shield and trimmed to
the ehleld's shape.
On the back Of the shield IL a human
acting plecs Of mechanism which picks
up a ton segment OF a ring and tacks II IN
position. Workmen follow pounding In
Leaving the shields behind the party
stumped on IN their rather large rubber
boots, 70 the uproarious delight OF the real
EroundhoRs. who looked up from their
work TO see the sight. On each side OF the
roadway the visitors now found concrete
trenches, broad and smooth. Under these,
they were told. run the oonduitg for cleo
trio light and power, The trenches them
selves form a convenient sidewalk for
passengers in the event Of trains being
stalled In the tunnel and are high enough
TO keep the said passengers feet dry in
something of flood,
One Of the pretty engineering problems
faced BY Mr.. NOR and HE assistants came
from the fact that the strata Of rock on
each side Of the river sloped down, causing
the tunnels 10 emerge into boulders and
quick sand, and ultimately silt and quick
sand without boulders. Through the Man
o'-War's reef there waB seldom sufficient
rock In the roof Of the tunnel to form a
safe cover.
II enough air pressure was used TO hold
back the uuicksand and water the con
tractors were confronted with the risk Of
blowing Cd the roof Of the tunnel, 90 weak
was the resistance, An accident Of this
kind In which a workman was projected
up, through and out Of the river above
occurred in the construction ofthe Brook Ign
tubes.
Mr.. NOR had arranged for this contin-
Rency, and by permission Of the War De-
partment half a million cubic yards Of clay
was dumped into the river over the tunnel
path. This clay blanket furnished the
required resistance 10 the air pressure from
below, made possible the work, and Is now
being dredged on again.
To the stranger all four tubes are A alike
as the backs Of a deck Of playing cards.
A.at, Az sNaitara pItsafaEgH m the roof ni
the tube, again they stalked Indian file
along a swinging safety walk. The guard
rail had been removed from this one pre-
paratory TO tearing it down, but they had
learned how TO walk on the sensitive path
and didn't mind. .
Again they entered an air chamber and
submitted 10 e reversal Of the first process.
The decomposition Of the air Ia not At
first the relief 70 unframed ears that II
might seem. One has the feeling that
air bubbles are emerging from his ears,
lodging in some mysterious way through
his ear drums. The process was divided
between two chambers az the compression
had been.
Compression makes hot places Of air
chambers and even Of big iron tubes. When
the indicator in the corner Of the chamber
swung back toward zero-the pressure OF
the outside air-the old timers in the party
turned up their collars and buttoned their
coats. One OF two wound woollen mut1ers
about their threats,
In a moment the tenderfeet understood
their action, for with the decomposition
they we're coming into a comparative De-
The sun was still shining brightly
when the elevator landed them again at the
surface. and some Of them we're glad TO see
II after only an hour under the East River
at thirty-four pounds pressure to the square
inch.