New-York tribune., 1874-06-11

are spsces o Is sect nchss at Each extsrio.
has bottom Width Of feet srS oyss %rs ta 20
support the roadway above The position Of the spaces
fixed approximately that OF the permsnetns
derricks needed IN prosecuting the work The lines OF
bracing had also TO be xed with reference " the paces
and derrcks ordinary length Of spruce penks was
feet Of sheeting were decided upon
all points where the depth was not over Is feet ana
three where the dspth greater This liked the OK
IN: sjsS S feet res A. ass e the
bank opposite. it was necessary to o.,s6nvhls dvlds
ss t%Sss sns 80 the &C.
the system. without making necessary the use OF lncon
yenenty large eizes or ncreasug the % msnr
must be themselves supported at least once III ~ ,eet
aud that sfeet spaces only were Nine
each in the and front and IA on eacn sue ono9
diagonal braces could be used a. shown t5 hacin aod
lines of through transverse braclng. a. ne INTEL @
sections Of the main aes qua. to depth Of
about three tide. The excavation was tneh
pnt in as shown in section. After this was well under
way the second range Of sheetng was started on tne
come severe the braces between the heads Of the
piles wers pnt in each direction adm roIIn In tins
s1sy %Ss 'n' s i%0'H excavation in the central
being in tne last removed he popae are
carefny calculated and sizes proporuoned accordingly
AT three points the anchors to the derrSk Guys hau 20
be partly supported by the sheerng ana 'ae sizes o,
braciug were increased order 70 resist tho
Toe oe yeea aea aa two feet Tne
braces from the lowest strngers we're 'nGna% t @
there was at the bsenniur a clear working space of
soven feet tho greater portion OF tno auea, A
W ss also tnat the central spaces in which to
lower timber were II feet ~ "a feet wide anu 50 feet
S. feet long were 10 wered without difficulty o,. ,
Every precauton was taken 10 aecurasrp h uoa .ne
daponas and braces and TO elects wherc there was
danger of slipping and there was no failure at any
point. Notwithstanding some very sewers ira rams wnen
,i,,ia tl,a
from the rear bank was sufficient TO press the main
braces inch into the yellow pine pie' put ho ouDe
When It becomes necessary remove the long cross
ng rom the sringer to supporter down to the ma
sonry were pat in and securely fastened the long
ones were then taken out Win ehuro S"o'J'
USE or THE WATER JET
The sbee,ing was mostly twoinch stuff; small por-
ton only at an exposed Joint being thicker In driving
the lowest range Of sheeng great difficulty was found
in penetrating the fine. compaoed sand, below tho
water line After irving several devices. 1t was decided
to use TaseT nr"yds led aSos nSI . Jet from
pine feet loDg (wIth stopcock at ts upper endt
by ,s Ese the plank, were forced down very readily
six inches below tide was the average depth driven 10
enable us to overcome the feet OF the excava
ton 1t was necessary to pump tho water OUT
of the pit and the question arose as 10 tue SIZE OF
pump experiment was tried piece Of 8inc
sewcrppo was into the sand at the bottom OF
G % thc waer ude baed w out The time and depth below
the ton was then noted, and when nearly hled tne time
was again noted, together with the increase In hight
The average head under which the water entered did
not exceed SIX inches ana ~ was tnougnt 'nat uns
the sheetng Taking the relative perimeter OF the two
as basis to be pumped. about 80 gallons per minute
WORKING. the amount discharged was found to be 60
gallons per minute. This method would no doubt be
SD wero IN to be apprehended To facilitate the work
excavation two piles were driven little forward OF the
center of the pit and strongly braced 10 the adjacent
piles, on which derrick with IS feet OF boom was
erected With this the sand boxes would be handled ana
timber unloadei and lowered into the pit with
great facility The derrick was worked from
at cars su oienty strong bear load Of 10 tons The
boxes were very strong and proportoned 10 noia
which we're liked and one other. leading forward and
fastened to the bottom which had tripping arrange
a bolt which could be tripped by the same rope whcn
trpped the chain. The boxes were transported inll OF
to traveller inclined wire run up to an ee
vation OF 90 feet. dumped by tripping the aoot anu
cayation Tne arrangenent worked WE'LL and the cost
of doing the work was moderate the tempor@r1 aer Or
erected. and then removed. The maximum pressure
upon the sand underneath. caused by the complete
structure, VIII be about tons per square foot
LOWERING THE ANCHOR PLATES.
The only remaining point OF interest was the method
taken lower the four anchor plates Into the p Tnese
were massive castings III feet by I6 feet and ~ feet
deep lover alD and weighing % tons each. For this
purpose excavation 20 feet wde with slope OF two to
one was made In the rear, and hole cut through the
shee;ing. In this timDer-ways were laid and two
sticks were also bOted each OF the plates for sliding
pieces They were then lowered by tackle without
trouble This method was preferred to that OF lowering
direct on OF the expensive appliances required
s well Of the risk incurred BY bringing such weight
the bracng In conclnsion 1t Is only just to say tha
the work would have been comparatively simple had
there been Unlimited space for working The extremely
contracted space and danger OF undermining buildings
digging as IA feet below tho deepest fOu da
ton greatly increased the risks and difficulties OF the
work. These all overcome, however, and the ma
sonry has brought to the surface without detr
ment to surrounding property. and with no mishaps
from caying banks.