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18 AVIATION May, 1911 the pointer attached to a sphere, which, due to the wind pressure, moves over the graduated scale on the sector, divided to indicate meters per second of the wind velocity. This apparatus has no moving parts and the scale is divided to read by 1/2 meters per second, wind velocity. [[image - drawing of Hand Anemometer. Drawing by A. DUBRAY]] [[caption]] Hand Anemometer [[/caption]] Robinson's Whirling Anemometer. The rotating anemometer for aerodromes is to be fixed on a staff, about sixty feet above the earth, and the average speed in the wind by meters per second is determined by counting the number of turns per minute and dividing by ten. [[image - drawing of Robinson's Whirling Anemometer. Drawing by A. DUBRAY]] [[caption]] Robinson's Whirling Anemometer [[/caption]] Esnault-Pelterie Landing Indicator. This instrument consists of a registering cylinder revolving in four hours or 24 hours as desired. Two pencils are placed 90 degrees apart around the drums, tracing lines which will become wavy upon starting or landing. [[image - drawing of Esnault-Pelterie Landing Indicator]] [[caption]] Esnault-Pelterie Landing Indicator [[/caption]] DESCRIPTION. The landing indicator was devised by Mr. Robert Esnault-Pelterie and has the advantage of registering at the same time the duration of the flight of an aeroplane as well as the starting and landings. This apparatus consists of a revolving cylinder driven directly by a clock movement on which a sheet of paper is attached, and two pencils placed 90 degrees apart and attached flexibly to two supports. These pencils bear on the paper, making two lines which become wavy at each start and for each stop of the aeroplane. The instrument may be attached to the aeroplane frame and it is protected by a strong cover. Tachometer. This apparatus has long been used on automobiles nad is now particularly applied to aeroplanes for indicating the
