The machine is mounted on two wheels under the centre of the main plane, with a flexible wood skid projecting forward. Another skid is set under the tail. It is claimed for the Antoinette machine that its inherent stability makes it one of the easiest of all for the beginner in aviation. With as few as five lessons many pupils have become qualified pilots, even winning prizes against competitors of much wider experience. [Illustration: Diagrams showing comparative size and position of surfaces and structure of the Bleriot (left) and Antoinette (right) monoplanes.] THE SANTOS-DUMONT MONOPLANE. This little machine may be called the “runabout” of the aeroplanes. It has a spread of only 18 feet, and is but 20 feet in total length. Its weight is about 245 pounds. The main plane is divided into two wings, which are set at the body at a dihedral angle, but curve downward toward the tips, forming an arch. The depth of the wings at the tips is 6 feet. For a space on each side of the centre they are cut away to 5 feet in depth, to allow the propeller to be set within their forward edge. The total area of the main plane is 110 square feet. The tail-plane is composed of a vertical surface and a horizontal surface intersecting. It is arranged so that it may be tilted up or down to serve as an elevator, or from side to side as a rudder. Its horizontal surface has an area of about 12 square feet. The engine is placed above the main plane and the pilot’s seat below it. The body is triangular in section, with the apex uppermost, composed of three strong bamboo poles with cross-pieces held in place by aluminum sockets, and cross braced with piano wire. [Illustration: Santos-Dumont’s _La Demoiselle_ in flight.] The motor is of the opposed type, made by Darracq, weighing only 66 pounds, and developing 30 horse-power at 1,500 revolutions per minute. The propeller is of wood, 2-bladed, and being mounted directly on the shaft of the motor, revolves at the same velocity. The speed of the Santos-Dumont machine is 37 miles per hour. [Illustration: The Darracq motor and propeller of the Santos-Dumont machine. The conical tank in the rear of the pilot’s seat holds the gasoline.] The lateral balance is preserved by a lever which extends upward and enters a long pocket sewed on the back of the pilot’s coat. His leaning from side to side warps the rear edges of the wings at their tips. The elevator is moved by a lever, and the rudder by turning a wheel. While this machine has not made any extended flights, Santos-Dumont has travelled in the aggregate upward of 2,000 miles in one or another of this type. The plans, with full permission to any one to build from them, he gave to the public as his contribution to the advancement of aviation. Several manufacturers are supplying them at a cost much below that of an automobile. [Illustration: Sketch showing position of pilot in Santos-Dumont machine. _A_, main plane; _B_, tail plane; _C_, motor.]