Encyclopædia Britannica it is scarcely used, and reviewers have recommended that it be dropped from the encyclopaedia. The also has color transparencies of human anatomy and several appendices listing the staff members, advisors, and contributors to all three parts of the Britannica. Taken together, the and comprise roughly 40 million words and 24,000 images. The two-volume index has 2,350 pages, listing the 228,274 topics covered in the "Britannica", together with 474,675 subentries under those topics. The "Britannica" generally prefers British spelling over American; for example, it uses "colour" (not "color"), "centre" (not "center"), and "encyclopaedia" (not "encyclopedia"). However, there are exceptions to
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