The Sun.
London, England, 1864-05-20 00:00:00

'I IE HRIDGES AT BLACKFRIARS,

Tb e works connected with the magnificent rail-
way bridge for the London, Chatham, and Dover
lino acros a this part of the river are now so rapidly
advancing towards completion that even the casual
observer can mark the progress made from day to
day. Never even in London has a work of such
magnitude and such solidity been executed in so
short time. On the 2d of May last year the first
stone of the Surrey abutment was laid, and on the
3d of this month the last stone of the masonry on
the Middlesex side was completed. The line up to
the Holland-street side has been finished, and ap-
proved by the Government inspector, and will be
opened for traffic on the Ist of next month. Of
the bridge which will connect this great goods
station with the City terminus, two of the wrought-
iron spans are completely finished and standing
alone; the supports will be removed from the
third next week, and the fourth and fifth are well
begun, and will be completed in the course of a
month or six weeks at latest. The preliminary
tests for strain w:11 then be made by loading the
whole work with locomotives placed as close together
on all four lines of way as they can stand, and
then the bridge will be formally opened into the
temporary station at Ludgate-hill in the middle or
end of August next.
The extreme rapidity and simplicity of the mode
in which these huge wrought-iron spans are built in
place is just now curious to witness. Each span is
160 ft. long by 16ft. deep, and laid for two lines of
rails ; two such spans laid side by side form the
width of the structure, which is five spans, or a little
short of 900 ft. long. The method of building it is
by constructing what is called an American truss—
that is, a powerful lattice work of timber strength-
ened with iron tie-rods in every part ; in fact, nei-
ther more nor less than the cheap strong frame-
work on which the Americans carry all their rail-
roads across rivers. This truss, which is floored at
the bottom, and strong enough, to bear a load of
three tons per lined foot, is built with its endsrest-
ing just below the heads of the iron piers which are
to carry the permanent girders, the broad iron plates
of the bottoms of which are then laid in plats on
beams of timber to raise them from the floor of the
truss to just above a level with the heads of the
columns, and when fitted are loosely keyed together.
Once thus keyed in, the angle irons at the sides are
rivetted oa to prevent any lateral movement, and a
sound basement got at once on which to proceed
building up the cross-barred pieces, which can now
be seen in the finished spans, and which form the
struts and tie-rods, one to resist compression and the
other to meet the tensile strain. When these have
been raised to their full height of 16ft. the top flange
is fitted, keyed, and rivetted together simultaneously '
with that at the bottom, and the span incomplete and
ready to stand alone, though still resting on the
beams, which we have spoken of as supporting it on
the door of the truss. When the last rivet has been
driven these beams are knocked sway, and the
girder stands alone supporting its own weight, and
equal to any that is ever likely to come upon it,
for each span is built six times in excess of the
strength required to resist the proof strain which
will be put upon it by the Board of Trade, and
which proof strain i 3 itself calculated at more than
four times what the ordinary ex;gencies of metro-
politan railway traffic will ever bring upon it. Each
span is built with what is termed a five-inch cam-
ber—that is, it is arch-shaped, but the rise of the
arch is only five inches. Waen the last supports are
removed from under the span it comes down at
once two inches from its own weight of 600 tons,
and, instead of rising five inches towards the centre,
it only rises three. This dlminution of rise is caused
by the strain of its own weight, and is produced by
an infinitesimal but gmeral compression of all the
plates in the top flange we have spoken of, which at
once brings the structure to what are called its bear-
ings—that is, to a point beyond which its further

yield will be almost imperceptible, even under the
most ponderous weights. When a spin has thus
been completed and left to stand alone, another

American truss is built for the reception of the nett,
and so on, till all the five spans of the br;dge get
into various stages of progress at the same time.
Each span as we have stated, consists of two of these
ribs or girders laid side by side—that is, there are
two outer-rib girders, on which rest the crossbeams
far the floor, and the end of these crossbeams meet
on a middle girderovhich has thus to do extra duty,
and has therefore to be of proportionately extra
strength. All three girders are of the samo depth,
but the two outside have only a width of 3ft., while
the middle one has a width of 4ft. Gin. The tie-
reds and struts are placed at intervals of about4ft.
apart. The former are flat bands of iron, half an inch
thick, and varying in width by gradual increases as
the end of the lever is approached, and the strain
becomes heavier, from five inches wide to ten. The
struts may be known at once by th lattice-work of
iron between them to prevent their buckling or
moving in the slightest degree out of the line of the
compressive strain they have to meet. On the ties
there will be a tensile strain of five tons, on the
struts a compressive weight of three tons, and same

have been tested to six times that amount before

being put up. The cross floor between these ribs
• or girders is of equal strength. Theie cross girders,
all of wrought-iron, are at intervals of only four
feet apart, to correspond with the ties and struts,
white throughout the whole length of the bridge,
from end to end, run longitudinal girders placed so
as to support each rail of the permanent way. Thus,
therefore, the eross girders or beams of the floor
being placed at intervals of only four feet apart, and
being again intersected by the longitudinal beams
which carry the rails, divide the whole floor into a
seriee of square compartments of wrought-iroi of
great depth and of proportionate strength. Over
this cellular framework will be laid a thin wrought-
iron floor covered with asphalt, and over all the
sleepers and ballast for the roadway. Etch pair of
main ribs or girders is connected from the upper
flanges by cross ties, three to each span, which are
placed more to guard against lateral vibration than
anything else. The ends, too, of each pair of spans
where they reach the columns are left quite unfast-
ened, reefing. on roller frames. This leaves each
span to contract or expand as freely as the weather
may require, but the greatest difference between the
extreme of summer heat and depth of winter will
only make a difference of from 2etin. to 3in. in the
length of the whole structure. Whare these ends
of the girder-ribs meet, a very handsome raised cast
prtnel to be hereafter gilt and coloured, will conceal
their junction. Nearly all the lower works of the
piers and
groups of
icast-iron columns is finished,
only one group of columns on the Middlesex side
remaining to be placed, and these will be on end in
the course of a week.
The completed piers on the Surrey-side come out
with a remarkably bold and imposing effect now
that they are finished. Not the slightest subsidence
has taken place in any of these piers, though one
has been weighted to more than double the strain
which the group of three will have to carry. In fact,
with their foundations going 29 feet deep in the
London clay, nothing short of an earthquake could
now disturb them. The Surrey side station is
nearly finished, and all the buildings and arrange-
ments connected with this are as complete as regards
the facilities they offer to the public as the other
stations along, the line to Victoria. They are lite-
rally models of what such metropolitan stations
ought to be. The traditional clay-coloured timber-
seed has been replaced by lofty and ample waiting
rooms for first and second class passengers, and the
rooms themselves are not only solidly, but even
comfortably furnished. 01 the Middlesex side the
station in Bridge-street is progressing, and all the
foundations up to Skinner-street, See,-hill, are
placed. The abutments for the Ludgate-hill viaduct
are complete, and the beautiful iron work of this
formeny much-abuse 1 structure will be in place in
another month, Etch side of this bridge will carry
a light and handsome outer bridge for foot passen-
gers, communicating with a staircase in the abut-
ments, which will lead down to Ludgate-hill.
Tbst hideous eyesore—the wall of old Fleet Prison,
will be removed, and its place occupied by a hand-
some stetian, similar in lt s general appearance
and decoration to that on the Surrey side of the
Thames. In Bridgeestreet, also, will be a station
near about the site where the insaranco office
stood. It gives a fair idea of the cost which rail-

we.y companies incur when they enter tho city,
if we consider what the London, Chatham, and
Dover paid to get possession of this single office.
The building was new and handsome, and cost,
we believe, £12,000. It is stated that the rail-
way had to pay for this building and or compen-
sation for removal no less than £40,000, for which
they received in return £4OO for the old materials
of the structure.
The works connected with the removal of old
Blackfriars-bridge have made no ostensible progress
since we noticed them last winter. The temporary
bridge is quite complete, and has been complete for
now nearly two months ? but the public have been
deprived of its use because the contracts for re•
moving the old structure have not been signed.
It is earnestly to be desired that there may soon be
an end to the delays on this account, and that the
public may not only obtain the improved accommo-
dation of the temporary bridge, but may be relieved
as soon as possible from the risk which retaining
the old structure as a thoroughfare now entails on
all who use it. There is no denying the feet 'that
old Blackfriars-bridge is very unsafe, and liable to
become imminently dangerous at any moment. The
temporary bridge is and 'ails been ready for traffic
for some time past, so that there now seem scarcely
more than routine excuses for keeping it shut and
the old bridge open.

Naval and Military Intelligence,

THE NAVY.

The operation of testing one of the new hydraulic
machines, of a size larger than any hitherto in use
at either of the Royal dockyards, for bending the
enormous armour plates with which the sides of
the Bellerophon and Lord Warden will be encased,
took place at Chatham dockyard yesterday in the
presence of Capt. Stewart, C. 8., superintendent;
Mr. Thornton, master shipwright; Mr. Baker,
chief engineer; and other officials. The machine
tasted was manufactured by Messrs. Baillie and
Co., Millwall, and was one of the largest ever sent
oat by that firm. The trial was under the superin-
tendance of Mr. Westwood and Mr. Baillie, both of
whom were present to direct the working of the
machine. The plates operated upon were four of
the 4k-inch Lerd Warden slabs, sent in by Messrs.
John Brown and Co., of the Atlas Works, Shef-
field, the plates being of rolled iron. The hydraulic,
machine was worked by steam power, and within
three minutes after the pumps had been set in
motion the required curve was given to the plate,
which was only slightly heated before being placed
in the machine. The contract made by the Admi-
ralty with Messrs. Westwood and Baillie stipulates
that the hydraulic machines shall be capable of
bending plates of 9 inches in thickness when chilled,
but the machine tested yesterday is equal to bend-
ing plates up to 12 inches, and even to 14 inches,
should plates of the latter thickness ever require to
be operated upon.

In addition to the hired transports laden with
returned stores from the demolished fortress of
Corfu, already reported in The Sun, and which
occupy every available space for discharging their
cargoes at Woolwich Arsenal pier, the following
vessels, similarly freighted, have arrived, and
are awaiting berths alongside : The Ann
Duncan, the Thornhill, and the Tanaro. Cap-
tain Thorvildten, the master of the Tanaro, re-
ports that when within half a mile of Tarifa, on
the Spanish coast, he heard, as he thought, the
firing of a single musket from the shore. This was
immediately followed by a gun shot, which passed
completely through the hull of his vessel nearly
amidships, and within three or four inches of the
water's edge. The Tanaro then hoisted her ship's
colours and let go her anchor. A Spanish boat
with some officials on board soon after made her
appearance alongside, but they were unable to hold
any communication, as none of the parties were able
to make themselves intelligible to each other. After
patching up the breach made on either side of the
ship by the gunshot the Tanora resumed her
voyage.

The screw steam frigate Prince Consort, 35, Capt.
George 0. Willes, C. 8., was placed in No. 1 dock
at Keyham on Wednesday morning.
The screw steamship Warrior, 40, Capt. the Hon.
Arthur A. Cochrane, will be removed from the
Q iecn's dock, at Keyham, today.
TN ships of war on the Australian station at the
date of the last advices were the Harrier, 17, Capt.
Sullivan; the Miranda, 14, Capt. Jenkins; the
Eclipse, 4, Capt. Mayne; the Curagoa, 23, Commo•
dory Wiseman ; the Esk, 21, Capt. Hamilton ; and
the Falcon, 17, Capt. Parker. All these vessels
were at New Zealand,

The following appointments were made yester-
day at the Admiralty !—David Wilson to be Burg.
to the Wolverene and Thomas 11. Taylor to be surg.
to the Rinaldo.