The Londonderry sifter. (South Londonderry, Vt.) 1883-19??, 1889-10-17
A MAMMOT
The Largest In
Nes

ne Dig uTbWDT.
world over the Thames river. at Nav 49,
don, Conn.,. which is to usurp the oll-time
ferry at Groton, has been opened.
The construction of this bridge has
br ught into Use methods which will be
great value to the Lridge builders OF the flu
tur some OF which were entirely novel, as
mucn 20 as they were satisfactory and labT-
saving in the end
There was nc season Of the year when tfr
public or the managers OF the road couai
count upon gett ny through, either IRON tie
east OF Inc west, on time or anything APP
proximating the sch DUE. There have been
the sudden fogs and storms of summer,
which have delayed the old ferry boats and
there have been the blizz ,rds and 10 ;-packs
OF winter, which have m ide even the three
quarter OF mile ru from Gro on to New
Lon on an unmitgated nuisance and con
slant breaker of w stern connec ions. While
the public have been growing over this err
ry 81 stem, the raj road people have been
thoroug ly dissatisfied, and for S0years they
have be n 10 king f relief such as only
bridge could afford.
The bridge crosses the Thames river at its
narrowest point. The entire super. tructure
is OF steel he draw is SOB feet long, and
the bridge is the long st double-track draw
bridge in the world. Two clear paS>ageways
of 225 feet each are afforded vessels. The
d aver is fanked on either side by spans of
30 feet and there are two other spans at
either side of the river LOO feet each making
the total length Of the superstructure 1923
feet.
But more interesting than the superstIuc-
ture is the substIucture. The depth of water
where the foundations of the abutments and
piers are placed ranges from feet to 81 fee
at low water and the depth of soft mud and
psnetrab clay mixed with shells is from 10
feet to 80 feet Turee of the piers upon
which the bridge rests have depths of water
and mud of 1870 1928 and 103 feet respectively.
The ear headway unior III brilge is 30
fe t, which allows the passage OF small craft
without orening the draw. The draw,
VIII CHI rests on steel wheels is operated by
steam power. The mechanism Of the urn
table the o.clating engines, and the ap-
raratus fer cking the bi idge and rails, are
Of the most approved patterns, 4 nd, Coupled
with the automatic electric signal system,
render the pasSag of trains ac oSs the bridge
as safe as human ingenuity can devise. The
draw weighs 1900 tons, or z, 800, 600 pounds
The bridge is prop, r,oned for moving
load on each track of two Seton consolidat ed
/ com tives, followed by train load Of 5000
pounds per foot.
The work of preparing the foundation
for the piers involved the construct on of
cribs for the sinking of the masonry,
which were larger an many of the tene-
ment houses erected in the principal cities
OF this country. One of the cribs wa
70 feet high and II feet square, and
these monster wooden frames were
towed out to midstream and sunk over
| pilIng foundations wnicl have surprised all
who have learned what was done to secure
the resting pl c's The piling, as above
! stated, was driven into mud 81 feet deep al
places To each pile, as it was placed in
position, was attach d a cord with a float tC
secure tine Identification Of each stick. Tbi
was done by a diver, ard then, wins
the time came to saw off the piles 81
as to furnish a level foun dation for the
cribs, long shafting was attached to a pc.
culiarly cons ructed frame and this was
sunk 81 fe4t, SO tn 1t the lower end of the
shaft, on which was a circular saw, was just
above the surface of the mud The saw was
then brought up against the pile, and, being
rapidly driven by a powerful engine. The
stick would be cut off at the desired place,
the cord referred to indicating with uner-
ring cert 'inty the operation of the saw.
When this Geep water w TX was completed
1t was (, und that the tops Of the piles, as lei
by the saw. did not vary more than one
quarter of an inch, a remarkable thing wher
the Disadvantages of swift and a changing
tide are nsidered.
The drawer was tui ned for the first time
few days ago, and, to che delight of th'
Drluga employees, tne measurements lnaue bl
oil. Monroe, who has had entire charge o
this stipend us Undertaking, were so accu
rate that the draw swung into tho sh n
ends and locked perfectly the first trial TIT
ends of the araw were meastI ed, but ther'
could not he found the variation of the 20ti
of al inch from the lines witch had beeI
laid down for the work. The structure wa
| given railroad test of six locomotives an
long string of h avilv loaded car Their
wa' no al probable deviation, objection Of
sinking, and the test was declared to be sat
| isfactory.
TIL WIS but one faf alitv on the bridg'
during the work OF corstru ton, and tina
wa lie death of youn man which &C
CT re las week, just a his y rticnlar EN-
plo ment wa, about concl ded He ! a
cen enca ed as a plinter since the construc
| ton begar. an at the tine Of his mis-
hap had fastened a 'ope to ok and in
/ tend ID to Site down e. the fl or of III
bridge. Tn rope slipp d, and ne fell 81 feet
me ting wi h instant 1eath
Col Mour and lis cprps of young en-
pin ers iii be at worl- on the bril- e abou
m,nih longer, 10 king alter Diet lis an
the little trings which must e ma So UT
tefore the 60 PAW accso the structure
I e is a Rhoie Islander ami a graduate Q
/ Brown University