D'Orcy, Ladislas. Aerial Navigation in The Mentor. Vol 7, No 7, May 15, 1919. 10pp illus article by the author plus 6 loose gravures, each two pages with a full page photo of Military Free Balloons, Naval Observation Balloon, British Naval Airship, Martin Bomber, USN Flying Boat, American Airmail Plane. Good; cover edge chips, spine loose, contents very good.