The Aeroplane Speaks. Fifth Edition

=Wind-Tunnel=--A large tube used for experimenting with surfaces and models, and through which a current of air is made to flow by artificial means. =Work=--Force × displacement. =Wind-Screen=--A small transparent screen mounted in front of the pilot to protect his face from the air pressure. Types of Aeroplanes. The first machine to fly--of which there is anything like authentic record--was the Ader "Avion," after which the more notable advances were made as shown above. The Henri Farman was the first widely used aeroplane. Above are shown the chief steps in its development. THE AVRO.--The aeroplane designed and built by Mr. A. V. Roe was the first successful heavier-than-air flying machine built by a British subject. Mr. Roe's progress may be followed in the picture, from his early "canard" biplane, through various triplanes, with 35 J.A.P. and 35 h.p. Green engines, to his successful tractor biplane with the same 35 h.p. Green, thence through the "totally enclosed" biplane 1912, with 60 h.p. Green, to the biplane 1913-14, with 80 h.p. Gnome. THE SOPWITH LAND-GOING BIPLANES.--The earliest was a pair of Wright planes with a fuselage added. Next was the famous tractor with 80 h.p. Gnome. Then the "tabloid" of 1913, which set a completely new fashion in aeroplane design. From this developed the Gordon-Bennett racer shown over date 1914. The gun-carrier was produced about the same time, and the later tractor biplane in a development of the famous 80 h.p. but with 100 h.p. monosoupape Gnome. THE MAURICE FARMAN.--First, 1909, the 50-60 h.p. Renault and coil-spring chassis. 1910, the same chassis with beginning of the characteristic bent-up skids. 1911 appeared the huge French Military Trials 3-seater; also the round-ended planes and tails and "Henry" type wheels. This developed, 1912, into the square-ended planes and upper tail, and long double-acting ailerons of the British Military Trials. The 1913 type had two rectangular tail-planes and better seating arrangements, known affectionately as the "mechanical cow"; the same year came the first "shorthorn," with two tail-planes and a low nacelle. This finally developed into the carefully streamlined "shorthorn" with the raised nacelle and a single tail-plane.