LONDON (Reuters) - London's Natural History Museum has installed a four-and-a-half-tonne blue whale skeleton to tower over the heads of visitors, replacing the remains of a much-loved diplodocus known as Dippy. The whale's bones, which were bought in 1892 for 250 pounds, have been suspended mid-air with the head lowered and jaw gaping as if it is about to scoop up tourists. The 25-metre (82-foot) long skeleton will greet people as they enter the building's Hintze Hall from Friday - a new display highlighting the institution's conservation work. ...