The British Press; or, Morning Literary Advertiser.
London, England, 1825-07-12 00:00:00

MIMES TUNNEL.

This novel undertaking appears to excite it continually
Increasing intarekt. The %loiters Registry shows the names
of very many foreigners, and among them some eminent
for science. It lies, we believe, excited much curiosity,
and forms a frequent topic of conversation on the conti-
nent—a tunnel for Carriages beneath such a river as the
Thames being regarded as one, at least, of the various
wonders for which England has become such an olliect of
admiration.

Amongst the recent visiters have been his Royal High-
ness the Duke of Gloucester; and on Friday last the
Chairman and Directors received on their works his Royal
Highness the Duke of Cambridge and his Duchess, his
Royal Highness Prince Leopold, the Earl of Ilardwicke,
Mr. Secretary Peel and his brother, Mr. Dawson, M.l'.,
and many ladies in their party. The engineer, Mr. Brunel,
explained in the French language to the ladies the modes of,
operation. The Duke, the Prince, Mr. I'eel's brother, and
Mr. Dawson, descended to the bottom of the shaft (now I
excavated to nearly the lowest point) by the ladders in
common use by the workmen. They inspected with much
attention, and expressed their approbation of the whole
proce!ting, and were shown some of the masses of shells 'I
I still found in the centre of the thick stratum of clay.
Some of the ladies were lowered down the shaft in s suit-
able chair.

Against the gable-end of a house on the works, the Di-
rectors have caused to be built, in brick, a fac simile of the
perforation which will shortly be begun horizontally across
the river, in order to show more strikingly the proportion
of height and breadth for carriages, &c. &e. and which will
,be painted in perspective, and will hare a fine effect. The
new steam engine is expected to be very shortly a work,
and must greatly expedite the operations. The clay ex-
cavated is conveyed into a neighbouring field, and is
there converting into bricks of particular make, to he again
usfyil, in its new form, in the construction of this sub-
!Nitrous communication.

We have much pleasure in laying before our readers,
from an authentic smite:, in our present number come in-
teresting particulars of the above undertaking. In an age
so fruitful of enterprise as the present, it is, perhaps, hazard-
ing much to point out any particular work as one exceeding
all others in boldness of conception, or in difficulty of exe-
cuiion ; but, looking at the nature of the operation itself,
and the combination of talent, precaution, and vigilance,
necrsaary to perfect the work, we do not hesitate in giving
the opinion, that should the Thames Tunnel be effected,
the completion of it will form an era in the scientific annals
of this country, alike honourable to Mr. Brunel, whose
genius projected, and to the individuals whose property
secured, the accomplishment of this grand undertaking.
The rapid strides which our country is taking in all
that is great and good are truly wonderful. No sooner
does genius arise and project, whether in a Telford,
or in a Brunel, than the capital of the merchant is put in
motion, and works are executed which, to our forefathers,
would have appeared impossible, forming durable monu-
ments to the spirit and enterprise of the age in which
we live. Nor must we forget, in estimating the progress
which science is making in this country, the enlightened
commercial views now so generally acted upon. Restric-
tion, that enervator of the commercial soul, is breathing its
last gasp, is drawing in hideous form towards the grave;
and in its place is rising an enlightened and expanded feel-
ing. which sees individual good in the general good; and
which leads the merchant and the monied man cheerfully
and with confidence to produce their capital, to give effect
to the midnight labours of the philosopher and the man
of science.

To illustrate these remarks by a view of the great work
now under our consideration, we ask what age, except the
present, would have come forward with a subscription to
accomplish this mighty undertaking? It is obvious that a
devotion to the arts and sciences is diffusing itself widely
over all classes of society, effecting a bond of union between
the scholar and the merchant, the engineer and the capi-
talist, which is likely to raise this country to a pinnacle of
glory never before attained.
Nr ith these introductory observations, we give our
readers the following particulars of the projected work :
The tunnel will consist of two archways, and, in order
that there may be no obstruction tt carriages, those going
from the north to the south shore will pass through one,
while those from the south t e north will occupy the
other archway. The passag ill be macadamized, and
there will be distinct paths for foot passengers. In the
centre, between the two archways and dividing the two '
roads, will be a line of numerous arches of communication
spacious enough to admit of persons passing from one road
to the other; and in each of these arches will be fixed a
strong gas-light. The approaches to the entrance of the
tunnel will be by circular descents of easy declivity, not
exceeding four feet in every hundred. One smaller one
for pedestrians ; another larger one for carriages; and so
easy will the descent be, that the heaviest loaded waggon
will never need to have the wheel locked. The descent
from the north side will be near to the end of Old
Gravel-lane, at the eastern end of the London Dock, and,
on the south side of the river from a spot near to
Itotherhithe Church. The bed of the river has been
rigidly examined by frequent and deep borings, in order
to ascertain the nature of the strata, and the results
have been, we are informed, highly encouraging; the
deep parts being uniformly of a tenacious, hard, blue clay.
The machinery, by which this excavation is to be made,
is the invention of Mr. Brunel. The iron shield, for the
protection of the workmen, and for the security of the
work as it proceeds, is of an ingenious combination, and
of itself is said to weigh ninety tons ; and this weight is
literally to be pushed through the earth, entering at the
shaft on the north side of the river. For this invention
Mr. Brunel has obtained a patent. As this large shield,
or three-staried iron scafrolding, is daily moved on to
fill up the excavation made by the workmen, is to be
followed closely by the bricklayers, who will make all
good ; so that the incumbent earth N All always be sup-
; ported by the iron shield, or by compact and well ce-
mented brickwork. 'f he size of the tunnel will be thirty-
; five feet wide, by twenty feet in height ; each archway will
have about fourteen feet clear width (including footpath);
and the whole length of the tunnel will be about one thou-
sand three hundred feet. Shoahl nothing unforeseen pre-
vent it, this novel communication is expected to be opened
in less than three years. It will he obvious to every per-
son acquainted with the Thames, that no bridge could crors
it where the tunnel is designed to he made, unless it were
of a height so great that ships could sail beneath it. Such
a bridge has been projected, but the design was soon
abandoned. The tunnel may be regarded as a bridge re-
versed, and as a channel of intercourse between the two
shores, at once commodious, and suited to its locality.
Such an intercourse has been for a long time a desideratum,
and mast, we conceive, be much used. It will open a
free, and probably an important, communication between
the counties of Middlesex, Essex, Kent, and Surrey, and
the several national and commercial establishments on
either shore, and which, in time, will give birth to im-
provements of no small magnitude. The laud is already,
we believe, regarded as more valuable, in the view of
this new channel of communication ; a new road and new
docks arc projected, and we have no doubt that, if
this shall succeed (as we firmly belim: from the persons
conducting the undertaking, and the talent employed, it
will) other tunnels will be hereafter undertaken; and so,
without interrupting the navigation of the Thames, its
stream will hereafter be no bar to the easy intercourse he-
r, tween the shores, even by carriages of the largest tlescrip-
lion, and for loads of the heaviest weight. There will
:I be in this tunnel a thickness of fifteen feet of earth be.
' tween the crown of the tunnel and the bed of the river ;
and the brick-work will necessarily be of the best ma-
Iterials and most solid nature, and closely cemented with
the utmost care. _ _ _

The present is not the first attempt which has been
made to carry a tunnel under the Thames. Some years
ago such a work was projected at a part of the river
near Gravcsetal, but the attempt proved abortive. An
attempt was made near notherhithe in 1809, which also
failed. The improvements which have since that period
been introduced by Mr. Brunel into the science of tunnel-
ing, incline us to look for a more fortunate result from the
present attempt. The following is a description of the
mode adopted in carrying the work into effect, as set forth
in Mr. ltrunel's plan.
In the case of the drift-way made under the Thame
at notherhithe, in 1809, the water presented no obstacle
for nine hundred and thirty feet, when a great body
of quick-sand gave way, and filled the drift. The

ininers soon °relearns this obstruction, and were able
to proceed until they were, stopped by a second erup-
tion, "flitch in a few !nitrates filled it. Nothing comes
more satisfactory in support of the system that is adapt-
ed here, than the result of the operations that were Camel
on, under the most disadvantagens circumstances to
an extent of one thousand and eleven feet, and within
one hundred end thirty fOet from the opposite shore.
It is to he remarked, that at the second eruption, on
examining the bed of the river' a hole was discovered, four,
feet in diameter and nine feet deep, with the sides perpen-
theater ; a proof that the body of quick-sand was not exten-
sive. But what is most mina:l:able ie, that this hole could
be stopped merely by throwing from above * 'quantity of
clay, partly in bags, and other materials ; and after pump-
ing the water out, under a head of twenty-five feet of loose
ground, and thirty feet of water, the miners resumed the
the work, and proceeded a little further; but finding the
bole at the first eruption increased, and the filling over
the second very much sunk, the undertaking was aban-
doned.

The peculiar character of the plan before us consists in
the mode of effecting the excavation_ by removing no more
earth than is to be replaced by the body of the tunnel, re-
' taining thereby the surrounding ground in its natural state
of density and solidity.
In order so to effect an excavation of thirty-five feet
in breadth by twenty-five feet in height, Mr. Brunel pro-
poses to have the body of the tunnel preceded by a strong
framing of corresponding dimensions. The object of
'lthis framing is to support the ground, not only in front
of the tunnel, but to protect at the same time the work
of excavation on all sides. The body of the tunnel,
which is to be constructed of brick, Is intended to be fitted
close to the ground; and in proportion as the framing is
moved forward, so the brick work is made to keep pace
with it. But, as this framing could not be forced forward
all in one body on account of the friction of its external
sides against the surrounding-earth, it is composed of twelve
perpendicular frames, which admit of being moved singly
and independently of each other, in proportion as the
ground is worked away in front. These several heroes
are provided with such mechanism as may be necessary to
move them forward, as well as to secure them against the
brickwork when they are stationary. It is to be observed,
that six alternate frames are stationary, while the six in-
termediate ones are left free, for the purpose of being
moved forward when required ; these, in their turn, are
made stationary for relieving the six alternate ones, and so
on. Thus the progressive movement of the framing can
readily be effected.
In order that a sufficient number of hands may be em-
ployed together with effect and security, each frame is
divided into three small distinct apartments, which may
properly be denominated cells. By this disposition the
twelve frames form thirty-six cells, in which the men
are to operate for excavating the ground. It is to be ob-
served, that the ground in front of etch cell is to be kept
from falling in by means of a powerful shield, consisting of
small boards, strongly secured by the frames. It is from
within the cells that each workman is to cut out the ground,
just in the way he would do if he were to cut out a recess
in a wall for the purpose of fitting a closet into it ; but,
with this precaution, that he is to remove each board, one
after the other, and replace each in succession as he cute
the portion of the ground corresponding with it. When he
has thus gained from three to six inches over the whole
surface, (an operation which it is expected may be made
in all the cells nearly In the same time,) the frames are
moved forward, and so much of the brickwork added to
the body of the tunnel. Thus in intrinzhed and secure
eels, thirty-three men may be made to carry on an exca-
vation which is six hundred and thirty feet superficial area,
in regular order and uniform quantities, with as much
facility and safety as if one drift only of nineteen feet
square was to be opened by one man.
The drift carried under the Thames, in 1809, which was
about the size of one of these cells, proceeded at the rate
of four to ten feet per day. In the plan now proposed, it
was not intended the progress should exceed three feet per
day, because the work should proceed with mechanical uni-
formity in all the points together.
With regard to the line of operation, if we examine the
nature of the ground the work has to go through, we ob-
serve under the third stratum, which has been found to
resist filtration from above, that the substrata, to the depth
of eighty-six feet, are of a nature that present no obstacle
to the progress of the wine!: we are informed that little
water was met there. It is therefore through these sub-
strata that it is proposed to penetrate, and to carry the
line that is to cross the deep and navigable part of the river,
leaving over the crown of the tunnel a head of earth of
from seventeen to twenty-five feet in thickness, quite un-
disturbed.

Admitting that in descending to, or ascending from,
that line, the engineer should come to a body of quick-
sand, such as that which was found within about two hun-
dred feet from the shore, it is then that the combination of
framing already described, would be employed with effect,
and accomplish upon a large scale, what is practised on
a very small one, by miners when they meet with similar
obstacles.

The nature of the ground under the bed of the river at
Rotherhithe in a line contiguous to that now proposed for
opening the tunnel, may be best understood by the follow-
ing tabular view

~,
Feet.
Greatest depth of water at high water - . - 34
The bottom of the river consists of a bed of gravel and sand,
the thickness of which is about . - - - 4
Clay mixed with sand - - - 2
- -
Stift clay . . . - . . • al

Total - 77
The boring tools have been forced into the soil to various
depths, but they have generally been broken by the adhe-
sive nature of the materials beneath ; and it is supposed
from the result of other borings made on shore, that the
ground is nearly the Fame to a considerable depth.
The cEimated expense of this undertaking, 160,0001.,
is so much under that of a hritip, as to have occasioned
doubts whether it has not been under-rated. But to re-
move these, it is sufficient to state, that it will be con-
structed almost entirely of brick, which is the cheapest of
I all building materials, not merely as a material, but also
in the labour; and though these are intended to be laid in
the beat Itt. .tan cement, in preference to ordinary mortar,
the cost of a rod of brick thus laid will not exceed 181. ex-
clusive of the labour ' • and as the length of the body of the
tunnel will be one thousand two hundred feet (a length
exceeding by much that of Westminster-bridge), it will
require one thousand two hundred and eighty rods of
bricks, the amount of which, at lsl. the rod, will be
23,0401., a sum that would scarcely pay for a single pier of
a substantial bridge: this will be sufficient to give some
idea of the cheapness of a structure which is composed en-
tirely of bricks.—Scientific Gazelle.