History of the Encyclopædia Britannica the criteria by which the articles were sorted were not obvious even to scholars, despite Dr. Adler's claims that the sorting followed naturally from the "Propædia's" outline of all knowledge. In 1985, the "Britannica" responded to reader requests by restoring the index as a two-volume set. The number of topics indexed by the "Britannica" has fluctuated from 500,000 (1985, the same as in 1954) to 400,000 (1989,1991) to 700,000 in the current 2007 print version. Presumably, this recent increase reflects the introduction of efficient electronic indexing, since the size of the encyclopedia has remained nearly constant at approximately 40 million
Skyscraper which passed their practical limit in 1891 with Chicago's Monadnock Building. The Council on Tall Buildings and Urban Habitat defines skyscrapers as those buildings which reach or exceed in height. Others in the United States and Europe also draw the lower limit of a skyscraper at . The Emporis Standards Committee defines a high-rise building as "a multi-story structure between 35–100 meters tall, or a building of unknown height from 12–39 floors" and a skyscraper as "a multi-story building whose architectural height is at least ." Some structural engineers define a highrise as any vertical construction for which wind is