The Penn's Grove record., 1921-11-04

t0p Cor roof, all of strong steel, well
bolted and braced and made alright
bycalking, and with cross walls so
that under the reof there would be
five rooms or "chamberS," each about
twenty-five feet wide by siXty-tive feet
long. The floor of each room would
he the dirt or sand of the river bank.
Let Us cut five holes in the roof OF
each chamber large enough to permtG
Of workmen and eNcavating tubs going
in and out.
Let the workmen dig into the dirt
forming the floor until an excavation,
say one foot deep, has been made over
the entire floor space of the i've
rooms. When this excavation is eX-
tended under the side walls, or prac-
ticaIly when the earth under the side
walls is looSened by picks. and the
support Of the walls is undermined
ana the whole box will settle. If it
settles out of level, toe much at n
side. then the workmen can bring the
box to a level position by stopping
work on the low side and continuing
10 dig under the high side. If the frlc-
ton between the outside of the box
and the sides of the excavation be-
comes too great for the weight of the
box to overcome, then the box u be
weighted.
Reinforced Roof
The weight required to continually
force the box down into the eXeava-
ton Is conveniently and economically
secured by the construction of the ma
sonry pier directly on top of the box.
AS the lower part of Our imaginary pier
may best be composed Of concrete, it is
evidently necessary to reinforce the
roof so it will safely carry the weight
of the soft concrete and also to build a
strong exterior wall or form to shape
and support the concrete and inciden-
tally to range so that the roles
through the roof are not closed by the
concrete. These requirements are met
by a structure placed on top of the
working chamber Cor b0X), which in
the language used by the workmen. is
known as the crib" The crib includes
four exterior walls of heavy timbers
forming the side and end walls inside
of whoch the concrete will be placed,
connected to the roof and to each other
by four longitudinal trusseS. much like
old fashioned timber bridge t%russes,
running the full length of the pier, and
twelve short trusSes running across the
pier (serving to Stiffen the roof, and
also there should be many cross tim
bers connecting the side walls and
many longitudinal timbers connecting
the end walls. all tending to stiffen the
outside walls and the roof.
Entering the Lock
If the lower door is closed. men can
first enter the lock from the outside
through the upper door; secondly,
close the upper door, and, thirdly,
open d small valve admitting compress.
ed air until the pressure in the lock
equals the pressure in the working
chambers fourthly open the uoor and
finally pass through the lower door
and the Shaft into the working cham
Der. At no time has there been il di-
rect open p~aSSageWar for the move
ment of air between the working
chamber and tire outside atmosphere.
Men leaving the working chamber 20
through The lower door into the lock
(the upper door being closed) second
~, close the lower door; thirdly, al
low the compressed air in the lock be
tween the two doors to escape until
the pressure in the lock equals the
outside or atmospheric pressure, and,
finally, when the pressure inside the
lock is equaliZed to the outer pres
sure they open the upper door and
are Tree to climb out of the lock into
the natural atmosphere. Again there
has been no time at which there was
a direct p~aSsageWay for the compress
ed air to escape from the working
chambers. The operation of the locks
specially arranged for passing the eX-
cavating tubs is the same in theory,
but in the type Of ~eNcavating lock gen
orally used NnoWn as the Moran
Lock-, the upper door or doors close
tightly around the wire rope which
carries the tub for ~eXeavated mate
rial. The operation is as follows:
The lower door being closed, the tub
il lowered into HE lock, the upper
doors are closed around the rope (the
tub being held in suspension by tire
ropo), the lock is then filled with com
pressed air until The pressure equals
that in the working chamber, when the
lever door can be opened and the tub
lowered into the working chamber to
be filled by the Workmen. When filled
the tub is hoisted into the lock, the
lower door closed, the air pressure Of
the lock reduced to atmospheric pres
sure, permitting the upper door to open
and the hosting Of the tub out of the
lock. When the bottom of the wall of
the working chamber is only a few
feet below water level the air pressure
need be only sufficient to balance the
slight water pressure. As the depth
increases the air pressure increases
correspondingly. For each foot of
depth below the surface of the water