Principal developments along the lines of the HS, H-16 and F-5-L types of seaplane, which were used during the war for convoy work, submarine patrol and scouting, are represented by present types PN-7, equipped with Wright T-2 engines, and PN-8, having Wright T-3 engines, a metal hull and metal tail-surfaces. Brief statements about their construction and performance are made and the subject of metal floats for seaplanes is discussed. “Training,” scouting and other types of seaplane are mentioned, and outlines given of their characteristics and performance.Launching airplanes from a catapult is described, some details of the development of the apparatus being given, and reference is made to a late development in which the catapult is actuated by the explosion of a powder charge instead of being operated by compressed air. Aircraft engine, propeller and accessory developments, seagoing aircraft-carriers and lighter-than-air craft are treated also, and numerous illustrations are presented.Principal developments along the lines of the HS, H-16 and F-5-L types of seaplane, which were used during the war for convoy work, submarine patrol and scouting, are represented by present types PN-7, equipped with Wright T-2 engines, and PN-8, having Wright T-3 engines, a metal hull and metal tail-surfaces. Brief statements about their construction and performance are made and the subject of metal floats for seaplanes is discussed. “Training,” scouting and other types of seaplane are mentioned, and outlines given of their characteristics and performance.Launching airplanes from a catapult is described, some details of the development of the apparatus being given, and reference is made to a late development in which the catapult is actuated by the explosion of a powder charge instead of being operated by compressed air. Aircraft engine, propeller and accessory developments, seagoing aircraft-carriers and lighter-than-air craft are treated also, and numerous illustrations are presented.