three-island principle

File:Exeter City (1887).jpg (1887) of the Bristol City Line was built using the three-island principle.{{cite book|author=Greenway, Ambrose|author-link=Ambrose Greenway, 4th Baron Greenway|title=Cargo Liners: An Illustrated History|url=https://books.google.com/books?id=Spj9AwAAQBAJ&pg=PA15|year=2011|publisher=Seaforth Publishing|location=Barnsley|isbn=978-1-78346-929-1|page=15}}]]

The three-island principle was a technique used in the construction of steel-hulled ships whereby a ship was built with a forecastle, bridge deck, and poop.{{cite book|author=Schäuffelen, Otmar|title=Chapman Great Sailing Ships of the World|url=https://books.google.com/books?id=QgMRudqoLGQC&pg=PA293|year=2005|publisher=Hearst Books|location=New York|isbn=978-1-58816-384-4|page=293}} The technique allowed the economical and efficient construction of ships and was particularly common in tramp steamers and smaller vessels of the nineteenth and early twentieth centuries. The Knight of Malta, for instance, a 1929 steam ferry of only 16 ft draught that operated between Malta and Sicily, was built on the principle.{{cite book|author=Greenway, Ambrose|title=Cross Channel and Short Sea Ferries: An Illustrated History|url=https://books.google.com/books?id=Jh1vBQAAQBAJ&pg=PA123|year=2013|publisher=Seaforth Publishing|location=Barnsley|isbn=978-1-4738-4492-6|page=123}}