The British Press; or, Morning Literary Advertiser.
London, England, 1819-04-13 00:00:00

THE MENAI STRATA

EXTRACT FROM PARLIAMENTARY PAPERS.

Nu. I.

Report, Plan, and Estimate, for a Bridge over the
Nlettai Strait, near Banzur Ferry

At all limes when the subject of improviser the great line
of cumin tttt ication between Dublin and hlder's has been
under considei alio.). the inconveniency and driller attend.
ing the passing the Menai Streit, which 'sepias air a the Wand
faro Anelesr•a firms Carnarynnaliire, has listen conotaistly dig.
cussed, and 11 ttt rums Plans have been proposed, with the
• ii-er Of accompl.tbiug a r.•eular and wnebstructed passage,
mu the place uf the present Ferry.
shall nut •tt nip' 1,. detail what have been considered
imperfect or objectionable modes ; it stems golf! salient
:11 5:1), that in the year a 1810 anal 1811, plains of linden
mole of east iron, ef sufficient width of span awl height
of e•h•vation, not to obstruct the were prtlltOrir4l,
111111, after doe investigation •pinov.,l of he the c.mmitr,
of the House of Commons, at suitable for she road commu-
Meat ttttt , amid not tojneissies to the uavigation.
lu the plan upon Ibis principle, which, in ISM by order
of the Lords ..f tire Treasury, 1 furnished, and which con.
*Wed uf rine ilrell uf cast Iron uf five hundred feet span, and
one hundred feel above high water in he middle f the
arch, and which, although the least expensive or any east
iron bridge of dinar dimensions, was estimated to coat
127,33 If. The chief IlitTicully in constructing this bridge
11,1• fiXilse Weeper crate ring, which. f the iorhy bottom I
of the cle I, :Insl de tub mid sapidity of the tideway, could '
not be aceoniplisloal by ord.llllll y mean.: from below. 1 was
therefore led to substitute a new osoile of suspending the
croteriog (gem Omer; anal also.: with my plan of a bridge,
furnished a design for this roupotc. There designs were
engraved amid annexed to the Repos I of the Ciminsitter
of
the stincre of Como ttttt s upon the Holyhead Road, in 1811.
leo 11114, on brine applied to fur a designs for a bridge to
crux' the river 311ersey set Rostrorn, where it wee fleet's...l,y
to preserve a waterway of inc thousand fret to breadth, $
brisige upon the pm isscsple of +impression occurred to me as
the soda practicahle means, and wills that view I instituted
rigidly set of experiments twin coda of malleable iron,
viz ft thirty to Moe hundred feet so length, and him% owe.
wen. I. iI. of an in. Ii to two inclws diameter; and these both
ui g.. Oil In elementary parts, and als,. upon combined,
trait) by ambling am, partly by juitiling in a model. Ibe
1.111111. altars .alt uf these expeliments air detailed and rom-
an nted upon in an excellent Treatise on the Strengih of
Material., lately pnblislwd by Mr. Barlow, of the Royal
Military Ameletny at Woolwich.
' 'From those 1 had reason to conclude, that by mean. of
malleable iron properly combined, a substantial bridge of
one dolman.' feel might be constructed; sod accordingly
gave • design fur that purpose.
The facility and rcuisonay with which a bridge of this kind
may he coiestrweled, where the shareware hold and high. Ird
td consider it as peculiarly well adapted for pasaing the
Menai Strait a little to the westward of Banco' Ferry, N+l re
a east t moth of five hand eel feet spats had been houserly
proposed. I base therefore drawn a plan upon this prin.
ciple, for the ennxiderattuit of the Cumuanwirmers for int-
t.ri.Ving die Holyhead Road 11 consists of one upeniug
of upgrai,l. of five hundr, it feet in width, and a burdred
fret in height, between the high water lose and the lower
able of thee ea/Away; and the roadway horizontal this
height is uninterrupted for the whole fire hundred feet.
where the natural rock which forum the western abut-
ment now interposes. lint iu addition to this het hundred
fret, there are Nor arches to the western, and awe uu the
eastern *idea the nusu Opening, each fifty feet span, that ie,
soaking in all eight lionsileed and fifty fret of opining, all as
she wai ow the annexed drawing. This drawing also +hews,
flirt is reg r.l tit the wirigation, it is preferable 11/ any bridge
of :en aec:sed foe at, her ante the latter affords the full height
f ais t only in the middle, whereas the former,
a• has ju.,t lie. n olisesvemi, .lords the same full height fur
the whole of the Ist c Is,uldnd fret. In regal el to scummy,
thi.l.,isire, 1,11 11,/- p,hicipleof snapention, lira equally the
ate at I lease estionatid the expense wily at ;shout
430,000! ; and allowisig fus the partible rise in the price of
irun, and any rinforeseen limits!. to pmicuriud Atone, it can-
not aint•ilist to 1111/1! than 70,100ei. whereas ill.. cheapest ut
the arched fos 111 with east bun was neatly double that sum.
W.th respect to the facility uf r.s.ecutiusa, it must be eel-
dcat to soy ti• rs/UII, the least conversant midi mechanical
..hose., Piet the bridge part of the parer up gto this
el,snos. may he elleliltileitd u, a,ly readily as dm center•
illf 01.13 i of the same size fur of Cast iron.
The mastitis room a bridge upon the principle of
sien, tali Ise sattsf.seturily ascertained by previous expert-
because with a given I,uglh and curs attire, it is
ku„,,,a, thug malleable trues of a good quality can support a
certain WrIZIII more Ihsu its 111111, and therefore when the
‘ecizld to Ise upposted is known, w tar rule is obtained to
eirte smiste Ilse (pia oily of iron ',ignited, and the Emulates
of the qmility of rash separate portieres of iron to be employ-
ed, inn be ellectually proved. The must 4,11'11z31..,11! mode of
hinatiom may also Ire drier ttt i t led by similes mean.; soil
although I have already r my experiments forme el a plait
which ta practicable and substantial, yet I AO certainly,
during the • tbe 'untie woik is iuusitneting, claim the
privilege id repeating and t ate tiding may experiments, in
order to arrive at the must perfect mode dos proteiple is
seas. pubic ur.
_ _ - - - •

The principle I have herr recommended, of enroitrorling
bridges by sospensions, all hooch' lathes to loot gr°etaltypear-
tin
it in this country, is not new; tiny write iu existence
over riorrs and deep ravine • in !Ciotti America, previous to
the arrival of the bpaniairls On slim country; they hare beers
long carried to a meat extent w the East Indies said China,
soil of late years tight have been cotisirueted its North
America. If these, with very bite • materials mid work-
matiship, have 1,4,11 on some instances u job i„.0,0 somu
ears ii.,l in about btu) feel in length, it is certainly nut assuming
trio much In expecting e from British di xtrrily, upon
superior materials. I IS
wily Is few years ago that bridges of
cart iron, °Come hundred feet span were ventured upon wills
timidity, and now, although obey have its some insiances been
mismanaged by bungling constiucturs, they have in Where
been sticre•sfully extewled to 130, 140, and 240 feet arches,
with sc,reely any other approach to a niaxitnunt, than what
is deli rutiord by localily mot expense. But bridges upon
the principle of •utopension being simpler its the nianage-
wilt, and lunch 11111,e cups ilutisaus and economical, afford to
a certain esteem even still greater facilities than Otiose of cast
imu, End therefore promise to become of at least equal 411.
(Sigurd) THOMAS TELFORD.
Leaden, 3414 May, 1818.