when did the construction of the eiffel tower start and end
Eiffel Tower Work on the foundations started on 28 January 1887.[15] Those for the east and south legs were straightforward, with each leg resting on four 2 m (6.6 ft) concrete slabs, one for each of the principal girders of each leg. The west and north legs, being closer to the river Seine, were more complicated: each slab needed two piles installed by using compressed-air caissons 15 m (49 ft) long and 6 m (20 ft) in diameter driven to a depth of 22 m (72 ft)[16] to support the concrete slabs, which were 6 m (20 ft) thick. Each of these slabs supported a block of limestone with an inclined top to bear a supporting shoe for the ironwork.
Eiffel Tower Many innovations took place at the Eiffel Tower in the early 20th century. In 1910, Father Theodor Wulf measured radiant energy at the top and bottom of the tower. He found more at the top than expected, incidentally discovering what are known today as cosmic rays.[30] Just two years later, on 4 February 1912, Austrian tailor Franz Reichelt died after jumping from the first level of the tower (a height of 57 metres) to demonstrate his parachute design.[31] In 1914, at the outbreak of World War I, a radio transmitter located in the tower jammed German radio communications, seriously hindering their advance on Paris and contributing to the Allied victory at the First Battle of the Marne.[32] From 1925 to 1934, illuminated signs for Citroën adorned three of the tower's sides, making it the tallest advertising space in the world at the time.[citation needed] In April 1935, the tower was used to make experimental low-resolution television transmissions, using a shortwave transmitter of 200 watts power. On 17 November, an improved 180-line transmitter was installed.[33]
30 St Mary Axe After plans to build the 92-storey Millennium Tower were dropped, 30 St Mary Axe was designed by Norman Foster and Arup Group.[12] It was erected by Skanska, with construction commencing in 2001.[3]
The Orleans The Hotel and Casino opened in 1996. When the casino first opened, it did not perform up to expectations. In 1999 a major addition to the casino and other amenities were added. The success of these changes has been demonstrated by continued expansions in later years.