The Sun.
London, England, 1858-10-07 00:00:00

THE VIADUCT AT SALTASH.

About eight years ago all England was talking
of and Europe wondering at the importance and
magnitude of that great engineering work, the
Britannia-bridge. Since then viaducts and bridges
of all kinds and sizes, and each one possessing one
or more features of peculiar difficulty, have been
erected without notice or comment. We have grown
accustomed to the great strides with which our
engineers have advanced, and look with compara.
tive indifference on what in other countries would
be regardedjustly as national works—the standard
of what their mechanical or scientific skill could
ever accomplish. There needs no greater prof of
this than the case of the Saltash Viaduct, now
nearly built, but with which we have no doubt the
majority of our readers are so little acquainted as,
perhaps, to be even unaware of the precise part of
the United Kingdom in which Saltash is situate.
Nevertheless, in this obscure little village near Ply-
mouth, a bridge is being reared across the Tamar
which is second to none in the world, and which in
size and in engineering difficulties of construction
far surpasses even that of Anglesey.
The line for which this noble work has been un-
dertaken is the Cornwall Railway, a single pair of
rails running from Plymonth to Falmouth, and
which, with the exception of a mile or so, passes
entirely across the hills and lovely valleys of Corn-
wall. That the whole route presents one continued
series of engineering difficulties can well be under-
stood from the semi-mountainous nature of the
country which it crosses. In a short distance of
60 miles there are no less than seven tunnels and
43 viaducts—some of them 150 feet high, besides
cuttings. almost innumerable. The viaduct of all
others is, of course, that at Saltash, which at pre-
sent is unsurpassed by any in the world, and likely
to be so for years to come. Saltash itself is a poor
insignificant place enough, though not altogether
so 'much so as one would suppose from its appear-
ance. The mayor of it, we believe, is even a more
important public functionary than the Mayor of
Plymouth, of whom he takes precedence, and by
virtue of his office as Mayor of Saltash is also
coroner for the borough of Plymouth, and takes
cognisance of all violent and sudden deaths which
take place in Plymouth Sound. But though, pro-
bably, our readers may care little and have heard
less about Saltash Proper, it is likely henceforth to
receive a fair share of general attention, and we
can safely say, to those who will journey.down to
see the bridge, that the viaduct requires indeed to
be a fine one to attract their attention from the
lovely scenery of the valley of the Tamar, which
it crosses. The banks of this noble river narrow in
considerably as the stream reaches Saltash, and,
hemmed in there to half a mile or so, suddenly
widens out into as fine a sheet of water as any of its
kind in the kingdom, its distant banks covered with
cottages and fringed with undulating woodlands
down to the very edge. Across this narrow part of
the channel, where Saltash in picturesque dirt and
disarray straggles up the banks on one side, and a
steep hill covered with rock and rock-grown under-
woosl forms the other, the viaduct stretches high in
air. The briefest general way of describing it is to
say- that it consists of 19 spans or arches, 17 of
which are wider than the widest arches of West-
minster-bridge, and two, resting on a single cast-
iron pier of four columns in the centre of the river,
span the whole stream at one gigantic leap of 910
feet, or a loner distance than the breadth of the
Thames at Westminster. The total length of the
structure from end to end is 2,240 feet, very nearly
liPlf a mile—and 300 feet longer than the entire,
stretch of the Britannia-bridge. The greatest width
is only SO feet at basement, its greatest height from
foundation to summit no less than 260 feet, or 50ft.
higher than the summit of the Monument. The
Britannia-bridge, both in size, purpose, and engi-
neering importance seems to offer the best compari-
son with that at Saltash, but the similarity between
the structures is far from being as great as might be
at first supposed. The Britannia tube is smaller, and
cost nearly four times the price of the Saltash Via-
duct, though the engineers had natural facilities
which Mr. Brunel for his Cornish bridge certainly
had not. The Menai tube is a pure suspension bridge,
and the main tower had a ready-made foundation in
the Britannia rock, from which the whole structure
now derives its name. To cross the Tamar with one
unsupported span nearly a quarter of a mile in length
was of course impossible, and Mr. Brunel had not
only to make his pier in the centre of the river, but
having no place to which to secure the tension
chains on which the roadway hung, had also to con-
trive to make them in a manner perfectly self-sup-
porting. For this the suspension chains hang down
front the piers in a segment of a circle, and are
bolted to the roadway, while above the road-
way, so as to form the other segment of the circle,
are two monstrous tubes of arched wrought iron,
connected with the ends of the chains, and which
precisely answer the purpose of metal bows. The
tubes and tension chains being connected with iron
trusses and both fastened to the roadway, the whole
acts as a double bow. As the tension chains give
under a strain they straighten down the bow above
them, and so the ends of the chains are supported
and kept in place, while the deflections of the tubes
themselves in turn relieve the roadway. It is very
difficult to convey to the general reader an accurate
and at the same time an intelligible description of
such complicated engineering works as these, and
perhaps the best and shortest way of showing the
nature of the difficulties that existed is to explain
how they were overcome, and in the actual progress
of the structure.

The 17 smaller spans, or arches if we may so call
them, which lead from the hills at either'side to the
edge of the Tamar in the centre of the valley, were
easily made, since they only consisted of double
columns of masonry, with wrought-iron longitudinal
beams of boiler-plate between them, for each side
of the roadway. The two main stone piers, which
at the water's edge on either side support the ends
of the great spans crossing the river, are of course
of a more solid kind, and well calculated to resist
either thrust or tension. Each of these is of masonry
29 feet wide by 47 feet thick, about 190 feet from
foundation to summit. It is, however, on the great
main pier, in the centre of the river, that all the
strain and pressure comes, and nothing short of the
solid rock would suffice for its foundation. To
reach this, however, was a matter of no ordinary
difficulty, as some 70 feet of water, with 20 feet of
mud and concrete gravel, lay between Mr. Brunel
and the stone on which he wished to build. A com-
mon cofferdam would be impossible in such a case,
but by a novel application of the cofferdam prin-
ciple the difficulty was overcome at last. An im-
mense wrought iron cylinder 37 feet in diameter,
100 feet high, and weighing 390 tons, was made
and exactly in the spot where the masonry was
to rise.. From this the water was pumped
out and air forced in ; the men descended, and,
working as in a huge diving-bell at the bottom of
the river, cleared away the mud and gravel till the
rock was reached. Steam airpumps were necessary
to keep the men supplied, and, as a matter of course,
they worked at a pressure of upwards of 381 b. to
the inch. At first this affected them severely; many
were seized with cramps, faintness, andinsensi-
bility, and one even died in a few minutes. But this
was only at the beg,inning., and after a time 40
labourers could remain at work at once in the huge
diving apparatus with apparently very little incon-
venience to themselves. It was, however, always
unpleasant labour, and all were glad when the first
great difficulty was overcome, and the solid column
of granite built inside the cylinder rose at last
above the water's edge.
On this noble pile of stone, springing many feet
below, the river's bed, the iron columns for the
centre pier were raised. Until these ponderous
masses were cast metal columns of such gigantic
dimensions were never dreamt of. There are four of
them, octagon in shape, 10 feet in diameter, and 100
feet high. The four stand each about 10 feet apart
from the other in the centre of the granite column,
so as to form a square of about 30 feet, binding the
four together in a handsome and massive lattice
work of wrought iron to prevent any lateral move-
ment. The weight of these columns is about 150
tons each. The way they were made was in 6-feet
Joints, each joint being cast in two separate pieces.
The thickness of the metal is two inches, and inside
each column is stayed and supported with massive
ribs. When all the pieces of the four columns
had been cast, each was planed down and fitted
together with the neatness of joiner's work. Thus
finished, all were sent off piecemeal to the centre
pier, though not erected, as they could only be
built up under the centre spans as the latter were
gradually lifted to their places by hydraulic pres-
sure in one gigantic piece weighing some 1,200 tons.
These two main spans or trusses consist each of a
wrought iron arched tube with two double sets of
tension chains attached to either end, which carry
the road for the railway. These, as we have said,
were put together at the river's bank, floated out
to their place, and then raised in one mass. The
process of raising them, for reasons we will men-
tion, occupies some five or six months. The western
span has been lifted to its place some time, the east-
ern is now in course of being raised, at the rate of
six feet per week. Each wrought iron arched tube
is elliptical in form, being 12 feet high by 17 feet
wide, and is made throughout of inch boiler
plate.. Inside, at intervals of every 20 feet, is a
wrought iron diaphragm,-and tie rods and angle
iron still further add to its strength. The curve of
the arch is 28 feet, and the tension chains at the
ends have, of course, the same. These chains are
similar in principle to those of an ordinary suspen-
sion bridge, except that,instead of being made with
links of seven bars, each link consists of 14 bars of
iron an inch thick and six inches wide. Each of
these chains has been tested with a tension train of
between three and four tons to the inch. Both

chain and tubes are connected by wrought iron
trusses to the roadway, the longitudinal beams of
which are braced together by transverse wrought
iron floor girders. When each span was completed,
before finally, lifting it to its place, the scaffoldings
were knocked away and the whole mass t( sted with
a deadweight strain, uniformly distributed, of
1,200 tons, which, with the weight of the truss
itself, was increased to about 2,300 tons. This load
was calculated to produce a strain of rather more
than 51 tons per inch of section of the tension
chain, and not quite 51, tons per inch of section of
the tube. Under this load the whole span deflected
seven inches, recovering itself in a few hours after
the mass was removed. The greatest strain which
the bridge can undergo when covered with ballast
to the depth of a foot and loaded with a train of
locomotive engines, will be less by, half a ton per
inch upon the chains and. tubes than the testing
strain we have mentioned.

When each span had been completed two iron
pontoons, each 50 feet long by 10 feet broad and
12 feet deep, were sunk under both ends, the water
let out of them at low tide, and with the return of
the flood the span was floated to the centre of the
stream. One was thus floated out about the middle
of last year, and one during last July, and it was
the unanimous opinion of all the many engineers
and nautical men who witnessed the operations
that they were about the best managed and most
successful attempts of this kind which had ever
been seen. The floating was, of course, managed in
an hour or so. Lifting themto their places,however,
has been and still is a long and most laborious ope-
ration. At each end of a span are two hydraulic
presses, of 22 and 11 in. diameter respectively, but,
of course, as these in raisinghave to carry the whole
weight of the spans, they require the most massive
foundations, so much so, in fact, that only those
which are built for the bridge itself will serve their
turn. Thus the span is floated to the centre of the
river, and rested at the height of the tide upon the
first six foot joints of the two iron columns in the
middle of the stream on one side, and the beginning
of the pier of masonry at the water's edge on the
other. Twice every week the whole span is lifted
in one day three feet, when the masonry, is built up
another three feet in three days, then the span gets
another lift, as before, making its total progress six
feet in a week. The iron columns placed under the
end in the stream pier are, however, in six feet
lengths, as we have said, so that only one can be
put under at one time each week.
rh this manner the west-end half was raised, the
two iron columns and masonry pier in that half of
the Tamar rising. as the bridge rose. Now the
eastern half is going up. in precisely the same man-
ner. When both are raised to the top the four iron
centre columns and side pieces of masonry will be
completed, though the two ends of the span will not
rest on the top of the columns, but upon a huge mass
of iron built on them, called a standard, and into
which the spans are bolted. This standard weighs
no less than 300 tons, and is built of five joints,
each joint like those in the columns, being 6 feet
high and weighing 40 tons. When the whole bridge
takes its bearings, as they are termed, the pressure
on the centre pier foundatton will be upwards of
eight tons to the foot, or double the pressure of the
whole mass of the Victoria Tower on its basement.
Any oscillating movement is counteracted by the
transverse floor girders, and the ballasting checks
a vibratory. motion. Six inches has been allowed
for expansion and contraction to each tube, but the
greatest difference yet observed between the hottest
and the coldest day has only made a difference of
two inches in the length of the bridge. The total
quantity of wrought iron in the bridge is 2,650 tons
—of cast iron about 1,200 tons, of masonry and
brickwork about 17,000 cubic yards, and of timber
about 14,000 cubic feet. Wherever the praise of
engineering works can penetrate the fame of Salt-
ash and its magnificent viaduct is likely to be still
more widely known even than the colossal work
which spans the Straits of Menai.

TOUSSOUN PASHA AT SOUTHAMPTON.

SOUTHAMPTON, WEDNESDAY.

The fine paddle-wheel steam-ship Faid Gihaad,
built some years since by the Peninsular and
Oriental Company as a yacht for the Pasha of
Egypt, has been in our docks for the last four
months undergoing a thorough refit and redecora-
tion under the company's superintendence. The
ship being now ready for sea, a state visit was paid
to her to-day by his Highness Toussoun Pasha, the
only son of his Highness Said Pasha, the present
Viceroy of Egypt. He was accompanied by Gal-
loway Bey (the Pasha's agent in England), Mrs.
Williams (his governess), a French medical officer,
and other gentlemen. The illustrious visitor and
his companions were conveyed in a small steamer to
the yacht, which was lying in the stream, decked
out in colours, and the yards manned by the crew,
who welcomed the young Prince with a shout in
their own language, resembling English cheers,
which, freely interpreted, was explained to mean,
" May Divine Providence grant you length of
days.!" On embarking in the Faid Gihaad the
captain and officers of the ship received him as a
guard of honour.. . _

- The young Prince, who is five Tears of age, is a
very handsome boy, thoroughly Vnglish in appear-
ance, of fair complexion, with a little colour, and
dark brown hair. His mother is a Circassian.
He was dressed in Turkish costume, with silver
epaulettes, band, and two stars, which, together
with the hilt of a small sword he carried, were pro-
fusely decorated with diamonds. He speaks French
and English like a native, with very little Turkish,
and exhibited much intelligence by the observations
he made in going over the vessel. He minutely in-
spected the ship in every part, and a State chair
was taken into the engine-room, in which he sat
for an hour, closely watching the action of the
machinery.
The yacht proceeded on a cruise down the river,
and passed Hyde, then returning to her moorings.
During the trip a sumptuous dejenner a lafourchette
was served in the grand saloon, which was presided
over by the youthful Pasha, supported by Galloway
Bey and the French medical gentleman above
mentioned. The health of the Viceroy and his son
was drank, which the latter acknowledged, by ex-
claiming in good English, " Gentlemen, I thank
you." Other toasts followed, and the captain and
officers of the Faid Gihaad were congratulated by
the English gentlemen present on the fact that not
one case of misconduct on the part of the crew had
been brought before the magistrates of the borough
during the four months that the vessel had been at
this port. Previously to the dejenner Capt. A. Kel-
lock (who represented the Peninsular and Oriental
Company on this interesting occasion), Mr. J. R.
Stebbing (one of the borough justices), Mr. P.
Hedger (dockmaster), and other gentlemen were
presented to the young Prince. His Highness, we
understand, remains in England another month,
and then proceeds to Egypt.
The Faid Gihaad is now fitted up in the most
superb style of Oriental magnificence. The grand
saloon, which occupies the full width of the ship, is
a truly gorgeous apartment, the great fault being
want of height to show it to proper advantage. It
is approached from the deck by a spacious staircase
of solid mahogany. The ceiling is composed entirely
of papier rnache in panellings, each containing a
handsome bouquet of flowers, or bunch of fruit, re-
lieved by gold beading between each of the panels,
which are beautifully shaped like shields. The
saloon is lighted at night by five sets of candelabra
branching from columns running from the floor to
the ceiling, each candelabra having 12 candlesticks
over which are suspended bell-shaped shades, hang-
ing by chains from the ceiling, the whole in electro-
plate, including the columns. The hangings are of
the richest character, comprising cerise, rose, and
white-figured brocaded Queen silk damask curtains
for the windows which light the apartment trim-
med with rich silk gymp, and lined with plain
crimson silk, in each case surmounted by a hand-
some sweep-shape ornamented cornice, in blue and
gold, profusely decorated with the star and crescent.
There are 36 ottoman seats in elaborately carved
frames, on four handsomely shaped and carved ca-
briole legs, French polished, spring stuffed with the
best hair in canvass, and covered with rose-coloured
morocco leather. Besides these, three large-sized
easy chairs, carved in the best Spanish maho-
gany, and similarly stuffed, stand in different parts
of the saloon ; while a capacious divan seat, con-
structed of the like materials, runs round the entire
sweep of the stern end of the saloon. Immense
mirrors are judiciously placed at either end, and on
the moveable blinds at the port windows are painted
transparencies of British vessels at anchor, Os-
borne-house, Cowes, Southampton, Egyptian
scenery, &c. Two state cabins open out of the
saloon, decorated in the Italian style, relieved with
beautifully-painted flowers and fruit, and gold, the
effect being remarkably chaste and tasteful. The
bathroom and lobby are painted white, with gold
ornaments, which is the Pasha's favourite style.
The papier Inache ceiling has been manufactured at
Birmingham, while the whole of the painting and
the gold cornices have been executed by Messrs.
Buchan and Son, of Southampton, and the upholstery
department was intrusted to Messrs. Perkins and
Sons, also of this town. A portion of the wains-
coting is executed in half-grained mahogany, so
delicately done as not to be distinguished from the
real wood, except on the closest examination. The
exterior of the ship is painted a light white, the
stern, bow, and paddleboxes respectively bearing
rich massive gold ornaments, the stern especially
being covered with a large eagle surrounded by a
trophy. Her steering compasses have been cor-
rected by Mr. Stebbing, and for the first time since
her construction they are reduced to a mere nominal
amount of error. The crew are all composed of

Turks and Egyptians, but the engine department
is intrusted to the care of Mr. M'Alpin and four of
his countrymen.
At the request of the Viceroy, the Paid Gihaad
will remain at this port during the winter, until
March next, it being too late for his Highness to
use her during the present season in the Mediter-
ranean. The officers and crew are ordered mean-
while to return to Alexandria, whither they will
proceed by the Peninsular and Oriental Company's
mail steamers Ripon and Sultan; and they are ex-
pected to return to this country in a steamship
built for the Pasha in America, which requires to
be greatly improved in speed, &c., and is to be
brought here for that purpose.