|Tower Bridge is one
London's great landmarks and 'The Tower Bridge Experience' is
one of the capital's most unusual and exciting exhibitions.
By the middle of the 19th century
traffic necessitated a new bridge close to the Tower of London.
The new bridge would serve the people of east London
who had to make lengthy detours across the capital to cross
the Thames at London Bridge.
A major problem was that the
new bridge had to be constructed to allow the passage of tall
ships into the Port of London. In 1878 the City Engineer,
Sir Horace Jones, suggested a double-leaf bascule bridge.
In 1885 an Act of Parliament was passed authorising the construction
of Tower Bridge. The Act stipulated that the bridge
be clad to match the style of the Tower of London.
Tower Bridge, one of the great
symbols of London, was built between 1886 - 94. Sir
Horace died shortly after the foundation work began and his
modified plan was carried out by Barry, assisted by Brunel
(the younger) and the resident engineer, Crutwell.
Two major piers were sunk into
the riverbed to support the construction. The piers are
185 ft long and 70 ft wide, with central areas of 70 ft square
forming the base of the towers. The main towers have
columns 120 ft high, while the smaller towers on the shore
have columns 44 ft high.
The 270 ft side spans are suspension
platforms supported by chains anchored in the rear of the
abutments and carried over the two smaller towers to the main
towers. Here they are joined by rods concealed in the
decorative wrought-iron of the two walkways. The towers
and linking catwalk provide support for the roadway's steam-operated
In all 11,000 tonnes of steel
were required for the framework of the towers and walkways
which was then clad in Cornish granite, with Portland stone
for the dressings and window mullions. This provided
protection the underlying steelwork and gave the bridge its
On its completion, Tower Bridge
was the world's largest and most sophisticated hydraulically
operated bridge. Until 1976 the winding machinery was
powered by steam but is now electronically operated.
The bascules, which were also replaced in 1976, each weigh
1,200 tons and have to be counterbalanced with 422 tons of
lead and iron. Taking around 3 - 5 minutes to open,
the bridge is 135 feet (40 m) high and 200 feet (60 m) wide
Because the Act of 1885 stipulated
that the public should have access over Tower Bridge at all
times, walkways were built between the towers, 143 feet above
the Thames. These enabled pedestrians to cross the bridge
even if the bridge was open for shipping. However, in
1910 the walkways were closed to the public because of the
large number of suicides.
During its first few years Tower
Bridge's bascules opened, on average, 22 times a day.
Today they still open at least once a day for large ships
or for special and historic occasions. Advance notice
must be given to the Bridge Master before the basules can
be raised. Call 020 7940 3984 to find out when it will
next be raised and the name and type of vessel passing beneath.
After a major renovation of Tower
Bridge in 1982 the walkways were glassed in and re-opened
as a tourist attraction. In 1984 a fascinating museum
about Tower Bridge opened on the south side of the bridge.
The tour ends in the pump rooms where the old steam
engines can still be seen.