The semi-weekly messenger. [volume] (Wilmington, N.C.) 1897-1908, 1906-09-18

James Forgie. a Scotchman. designed
the hydraulic sliding platforms with
which the shields are equipped II Is
on these platforms that the men stand
in making the excavations ahead Of
the tube itself: the platforms slide out
as the work advances, and the exca-
waited material is dumped Lack
through the shield upon tram cars.
which carry IL back to the SHAFT
Mr.. Forgie was the principal assis-
tant to the distinguished tunnel engi-
neer. Greathead, in the contraction Of
the Waterloo and City Railway tunnel
under the river Thames In 1894.
The contractors. the O'Rourke En-
cheering Construction Company. be-
gan operations in the subaque0us tun-
neis on April IS, 1904. the first boring
beginning on the Manhattan side. On
September ist operations on the New
Jersey side were begun. a deep shaft
having been sun on each sid prior 70
he beginning Of the actual boring.
Quietly the work went on. and the
public heard Of little that was hap
pening. Accidents were remarkably
few. There was only n death that
could be traced 10 the effects Of COM
pressed air; there were inevitably
cases Of the bends Two physicians
have been in constant attendance at
the works, and everybody who enters
one OF the tubes has 10 undergo q
rigid examination. Comfortable quart
ers. well heated and well ventilated.
are provided for the workers. and hot
coffee is given TO then. rs 2 Stircu-
liant, when they emerge ron COM
pressed air.
How q Tunnel i BoIei.
The tube itself consists Of a series
Of iron rings, and the installation Of
every ring means a progress 81 tW-O
and a half feet. Eleven plate : >
key piece To go at the to? complete
the circumference. and an entire ring
weighs about fifteen tons. The cast
iron plates. or sections o. the ring.
have nanges Ct right angles TO the
surface. and il is BY these hat thu
successive rings are held together with
bolts. Hydraulic rams, placed against
the f1anges every few inches around
the lube. push the shield forward at a
maximum pressure Of $500 tons: II
the pressure Of the air in h tube
be taken into o the pressure
upon the shield is increased to AGO
tons.
The shield itself weighs 1874 tons.
1t has nine doors in it. and through
these comes the rock, Or sand, or silt.
or whatever the material through
which the tube must be driven. Thirty
men work in a gang, and there are
three shifts in the day Of twenty-fOur
hours. The record progress so far is
Ave rings, or twelve and a half feet,
in eight hours. Men Of all rationale
! ties have built the Pennsylvania tubes
under the Hudson, gro having
J done a large part Of the job. LaZiness
is something the contractors never
had to contend with: they say there
must be something about the COM
pressed air which generates energy
and enthusiasm, for the "muckers'
vie with one another to make the
record number of rings.
Perhaps there has never been an
engineering project in which theory
and practice were so nearly in agree
ment. The engineers calculated the
difficulties closely, and a really re-
markable system of reports has been
in effect from the first day. Every
morning Mr.. Jacobs has known the
progress made the day before. to the
very inch, and the amount of rock
and soil eXcaVated, to the cubic foot
The Pennsylvania railroad officers and
the contractors hold this perfect sys-
tenn and the thOrOughness of each
days work chiefly responsible for the
prOmptneSs of the meeting of the
tubes.
Engineers say. too. that no project
was ever carried out where h en-
phasis was so entirely upon the results,
rather than upon the money i costs
to attain them. Records have been
kept with unprecedented accuracy
and f%ullness, and they have been cor
rected. revised and re-revised with be
NildcrinS frequency.