This photograph shows a Wright Flyer, possibly the one taken to France in 1907 by Wilbur Wright and assembled at the Leon Bolle factory at Le Maus. It became known as the "Wright A" and was used to give numerous demonstrations in France and established flying records for the era; on 31 December 1907 Wilbur made the largest flight to date (2 hr. 20 min. 23 sec.) and on 18 December reached a record height of 360 ft. The Paris label on the back of the photograph and the style of the launching derrick in the left foreground both suggest that this was one of Wilbur's flights in France.
The Wright brothers used the rail and derrick to assist the take-off of their aeroplanes from about 1904-08 and were sometimes criticised for doing so by those who believed that aeroplanes should take-off entirely under their own power. For launching, the aeroplanes, the twin skids (clearly visible under the lower mainplane) were mounted on a tandem wheeled dolly which had been placed on the monorail (about 100 ft. long and visible heading away to the left and behind the derrick). The derrick was equipped with a weight (lying on the ground within the base). This weight of about 15 cwt (800 kg.) was raised to the top of the derrick either by man power or a motor vehicle. A system of pulleys and a long rope than allowed the weight to be attached to a pin on the underside of the aeroplane. For take-off, the pilot applied full power to the engine and released the weight. As it fell, it pulled the aircraft along the monorail (away from the derrick) and the rope dropped away from the Wright when it was airborne. The technique proved extremely reliable, never failing in thousands of Wright take-offs. Historically, the system is of interest because the concept of assisted take-offs was subsequently used via a steam powered catapult for carrier borne take-off.
The Wright brothers eventually fell in line with emerging practice and fitted wheeled undercarriages to their machines from 1910.