floors were only accessible to employees and were environmentally controlled to protect books, many of which are old and fragile. The upper two stack floors occupied all the area under the dome. The fourth level, the Archive unit, was in the basement of the building. The lower two stack floors were smaller because the basement theatre took some of that area. In 2011 when the library closed for the alterations, there were 3600 stack columns supporting approximately 45,000 shelves; those columns were rooted in the sandstone rock underneath and supported the Great Hall's reinforced concrete floor. Placed end to end, those shelves would have covered over . The total floor area was about . After the 2010–2014 alterations, many of the former stack books (except rare or valuable or fragile books) are on public shelves. The library collections include over 30 incunabula (books published before 1500) and many first and early editions of major works. The special collections include: The Gaskell Collection – works by Elizabeth Gaskell, one of the most important writers to have lived and worked in the city The Theatre Collection – a record of the history of theatre in Manchester The Henry Watson Music library – one of the largest public library collections of sheet music, named after the Mancunian musician and composer Dr Henry Watson (1846-1911) who bequeathed his collection to the library. It was officially opened in 1947 by Sir John Barbirolli. The Newman Flower Collection of Handel Manuscripts – acquired from the estate of Sir Newman Flower by the Henry Watson Music library in 1965. This library of rare manuscripts had originally been collected by Charles Jennens, a close friend of George Frederic Handel, and was later held in the collection of the Earl of Aylesford. It contains works by Handel, as well as items of Italian music from the early 18th century, including concerto partbooks of the Four Seasons by Antonio Vivaldi. Notably, the collection also includes a number of previously unknown violin sonatas by Vivaldi, autographed by the composer, which are now known as The Manchester Sonatas. Library Theatre The Library Theatre occupied much of the basement of Manchester Central Library and was the home of the Library Theatre Company, a Manchester City Council service. It was built in 1934 as a lecture theatre, and since 1952 had been used by the Library Theatre Company. After the 2011–2014 alterations its area