The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1869-10-25
THE GREAT WORKS OF THE AGE.
The New Thames Tunnel-Its Extent, Econ
omy and Uses-How the Work Is Cnrried
On.

On.
From the London Times, Oct. 49,
The new Thames Tunnel has progressed so fast
since our last notice that it may be said to be
virtually complete, and will, 1t Is expected, be in
fit state for opening for public trafc about the mid
die or the end of next month. The whole length
from what may be called the summit OF Tower Hill
to the end OF Vine street. in T0oley street, on the
south side OF the river is just 1920 feet and Of this
distance more than 1880 feet has already been &C
compished and completed. only about forty feet
remain to make the junction with the Tooley street
shaft. This short distance, at the rate at which the
tunnel has advanced, could be accompl lshed In
about four or four and hall days. but the shalt Itself
cannot be ready within that time, nor indeed Is 1t
likely to be ready within the next fortnight. The
Hill by two feet. The former Is TO be tyeght feet,
whereas the latter is sixty feet Yet the Tower Hin
shaft was sunk quickly and without the smallest
difficulty. for after passing through about twenty
feet Of made earth the clay was reached little below
and not sign OF water was detected. WHAT we may
call the Tooiey street shaft is little ten feet
diameter, ana this has been sunk to depth or about
twenty feet, where has come upon bed OF gravel,
In which the water Is more abundant than could be
wished. 1t Is not however, in sufficient quantity to
prevent the shaft being very easily Kept dry by means
Of pumping but pumping is by no means wished in
this case, for the shaft Is very large build
inRs and to pump out much water from beneath
them would have the effect OF causing their founda-
diminished In bulk as the water was drawn or.
The Tooley street SHAFT therefore, Is being
sunk ca By 81 a Po'u used H
works OF this nature, and which brings up the
maximum Of gravel with the minimum OF water. In
this way the works are progressing steadily. AS far
as this shaft has yet gone. IL Is double lined with
iron casing. the inner rim OF iron keeping out the
OF the outer These iron rings OF the snat are Jour
feet deep each and they are forced by weights down
into the soil before much dredging out WITHIN their
circumference is attempted. Tue double iron lining
to this shaft will not, Is expected, be continued 10
much greater depth than II Is at present. There Is
haas ha hAAr hash
nearly passed and that the clay Will be reached.
When this attained only one lining Of iron rings
to the shaft VIII be used TO within lew feet the
bottom, where bricks faced with glazed tiles, 10
reflect the light, VIII be employed, as IN the shaft on
Tower Hi Night and day every four hours the
shield driving the tunnel moves forward eighteen
inches, so that there Is an advance OF nine feet m
every twenty-four hours.
The manner In when this rapid advance 10 accom-.
pshed Is rs simple and ingenious as 10 Is safe and
quick III It's mode OF operation. The snled Is a disk
OF mixed wrought and cast iron, weighing about
two aud hall tons. In the front next u tue clay
IL concave; III the rear where the men work, 1t looks
like gigantic cart wheel, having SIX spokes and an
open hollow felloe IN the centre. To this
shield, and extending backwards the men at
work. Is powerful rim, just like the cap 10 the
end of a telescope. Thus, the miners who work lI
excavate enough clay through the centre opening to
enable one man 10 pass III beyond the face OF the
shield, and he soon cuts away clay enough to find
room Tor Two, ana when conlrade joins him there
Is soon room made enough for three workers, but
seldom for more. The clay is OF the Kind well known
as the stiff London clay, OF a backisn green
color, just moist enough TO give 1t a thorough
tenacity, but without any water. When about
two ect have been excavated ali round In front or
the shield the miners return back through the cen
trail hole and with ordinary hand-screws they force
the shield on TO the length OF the distance they have
excaVdted. lts long rim still keeping them under
shelter as 1t IL advanced Within TINS rim segment
OF the iron tunnel is al built In three segments
eighteen incnes long, and on the process Is
repeated over and over again The inner face OF the
Shield Is so constructed TO receive the pressure OF
SIX scrcw'Jacks-one In eacn OF the Six spokes we
nave spoken OF. by these means a pressure oi sixty
tons could be brought to bear on tue whole shield
AS Il rule, however, one screw jack anu one man Is
suinclent to move IL forward, add this with ease.
Ia case OF any water being come TO, auch as
Sprln5-lor the Whole tunnel IL far below the bed
OF Tue RIVER water--it would yiye indications OF
lls presence III TIE moisture OF the clay long be-
fore the miners reached II. The course Of The exca
vall0ns OF The shield ABOUT 700 cubic yards OF the
London Gay nave neen dug out Tor the tunnel. alone.
This az fast as 1t was Gus out, was run IN little
'troleys'' to the Tower hi SHAFT and hosted up to
outer nir. But every 'troneyu dropped It's quantum
in the tunnel Till the base ol the tube became
covered with some six seven inches or sticky wet
clay. This has all been removed ana the tunnel,
as far as II has gone, Is clean from end to end.
Inc result H. that all that passes ON the
head Is ten times more oltnctiy heard than ever.
TIE passage or q steamer heard trtth noise so
oau ana uibrdttng In the at present confined air OF
the tunnel that II Is only the knowledge or the unal-
teraDie ana almost iinmovable strength Of the
STRUCTURE III Wnicn You stand that gives the nearer
confidence. Not only can every vessel be heard
passing-we speak OF course Of steamers large
or snaii-but even sncn sight noises as ham,
mering on the ships IN the Pool above can be
distinguished not only by the sound but even by
suo hiiRht tnouSh perceptDe vibration OF the ar.
Yet, the whole tunnel not only watertignt but
alright Inc tests taken for detection or any set
ucIent IN me IRON tuDe since II has been Duilt give
results that show stability that apparently nothing
uut an earthquake can unsettie. The greatest de-
Gect0D was only one-eigntn or an inch from the
true ieVe, anu In only two instances was IT oneslx
teentn AS lar as regards the tubes bearing pres.
sure they are equal now that they are formed in
circles 10 about ten times the pressure they can pos
siby have ~ bear. and TO more than twenty times
the pressure that Ii now laid on them. Altogether
about sei rings have now been laid and bedded in
win blue has cement. About twenty more rings
VIII couple the entire tunnel from Tower Hi! TO
lOoley street. the descent down the shafts
Will be W means Of nfts. These are 10
be constructed on special design OF Mr.. Barow's,
80 as, Ia case OF accident such as the giving way OF
any OF the apparatus, to clip the guiding rods and
cheek the progress OF the lift IN a few feet This
Invention, In TACT Is only very clever break, when,
instead Of actlDg instantly, and with sudden JERK
as bad as fail, slowly brings the MT TO standst
In about ten feet. THIS arrangement has one cs-
peciai merit which H. that 1t Is never likely TO DO
lower the INT 10 10 about nty times stronger than