The Sun.
London, England, 1864-12-12 00:00:00

single bar or plank of iron of each link in the chain. The
wire ropes are strong enough to support their weight till
they are joined in the middle, and thenceforth they sup-
port the-nselves. It is then simply a question of the cradle
travelling to and fro till all the bars of each link have been
added on, every additional bar, making the whole work
stronger. In the Hungerford-bridge only two chains were
used at each side—the bridge was only meant for passenger
traffic, and was only 14 feet wide. At Clifton the bridge
is 30 feet wide, and is intended for carriages, so
another chain has been added, making three at
each side. The chains at Clifton are made up,
as we had sail of odd and even numbers, alternately 10
and 11, each bar of each link in the three chains being 24ft.
long by 7in. broad and lin. thick. This gives a sectional
area of about 460 square inches of iron in the chains,
which, at the low estimate of 22 tons breaking strain to the
square inch of iron, gives, in round numbers, a weight of
10,000 tons to break the bridge down. The towers over
which these chains pass are built after the rough, massive,
and, if it must be said, somewhat uncouth style of Egyp-
tian architecture,—just such gigantic rock hewn porticoes
as one sees at Memphis and Thebes. There are arched
towers 48ft. wide by 30ft. thick, and 80ft. high. On the
Bristol side they only go down some 10ft. or 12ft. to meet
the rock, but on the opposite shore the shelving cmforma-
Lion of the strata requires a pile of masonry 100 ft. high
to meet the roadway above it. The bridge, which hangs
from the chains over the towers. is made by
tie rods 2in in diameter and Bft apart-81 in number on
each side of the structure. Each pair of tie rods have sus-
pended to them the cross girders which carry the floor Of
the roadway. These girders are 18in deep and 33ft long, and
like all the rest of the work are of wrought iron. The car-
riage way is 20ft wide, and the footways 51ft wide each, A
division 3ft high is formed between the roadway and the
footways by two long wrought iron girders 3ft deep by Bin
wide, which like two backbones stiffen the bridge from end
to end and stop the vibration which fierce storms would
otherwise assuredly occasion, as they once destroyed the
bridge at St John's. The curve or rise in the bridge is only
21ft at the centre. The saddles or rollers which let the
chains move over the towers meet the contraction and ex-
pansion. During a hot summer day the centre of the bridge
has risen 4in from this cause, and the difference between the
extreme of cold and heat makes an alteration of nearly lft in
the height of the centre. The arrangements made for com-
pensating this alteration caused by contraction and expan-
sion are very clearly explained in Mr Wright's pamphlet,
to which we have before alluded. He says :
" In all iron bridges, of whatever construction, it is ne-
cessary that provision should be made for the expansion or
contraction of the metal by heat and cold. How this is ef-
fected in the present case will be seen. Between a strongly
ribbed and massive cast iron basement and the main saddle
are interposed a double set of steel rollers, 41in diameter and
2ft long, the two sets being arranged side by side in a
frame, thus giving a rolling surface of rather more than 4ft
in breadth. These rollers allow of each saddle travelling to
and fro upon its basement according to the expansion of the
chains. To the main or lower saddle are attached the two
lower chains ; above the main saddle is bolted an auxiliary
or upper saddle, to which is attached the uppermost chain.
There are of course four similar saddler, one for each set of
chains at each tower; and the weight of each, with base-
ment, rollers, &c., complete, is about 30 tons. It has been
stated that each chain consists of several links arranged
side by side, and this will be understood at once on inspec-
tion, where the part of the chain attached to the saddle is
shown as it would be viewed,from above. It should also be
remarked that the chains are rather stronger near the towers
than in the centre of the bridge, the reason for which will
be seen at once in the fact that in the centre the links have
only to bear their share of the weight of the road, while at
the ends they have also to bear the weight of the chains.
To a certain distance from the towers, therefore, each chain
is composed, breadthwise, of 11 alternately with 12,
while towards the centre there are only 10 alternating with
11. Why the number of links in the chains is alternately
odd and even will be seen at once if three fingers be inter-
laced between four of the other hand ; the links are are
ranged in a precisely similar manner."
When tested the other day with a load of 500 tons of
stone on the bridge, the chains moved across their saddles
and lowered the crown of the centre seven inches, the
chains passing over the saddles an inch and a quarter on
each side. When the load was removed the bridge returned
to its normal position, nor did the most careful observation
with levels detect the slightest change. To all the common
modes of observation the whole structure seems as rigid as
stone to the passage of ordinary traffic.
As we have said, there are two suspension bridges made
of wire ropes of larger span than this bridge—the Niagara-
bridge, and the Fribourg, in Switzerland ; but the Clifton
is the longest and highest chain bridge in the world, and
the strongest suspension bridge ever erected. Its strength
the following figures will clearly show :

Ft. In
Span of bridge
Versed side of chains
Sq. in,
Sectional area of chains at piers
Do. at centre of chains
Tons.
Weight of chains between the piers
Do. of roadway
Tons.