The two main supporting planes in the regular Farman models were 33 feet by 6-1/2 feet, set 7 feet apart, and with a total area of 430 square feet. These dimensions have been varied slightly in other machines. The elevating rudder, which was set well out in front of the body of the machine, was a horizontal plane controlled by a wire and lever. In the rear was a tail of two parallel surfaces, slightly curved like the main planes of the biplanes. These two surfaces steadied the machine from front to rear. At their two sides were two vertical surfaces, giving the tail the appearance of a box kite, so familiar in the Voisin. These two vertical surfaces, however, comprised the direction rudder, and were turned from side to side by the operator with a foot lever. In some of the later Farman biplanes the two vertical surfaces were done away with in favour of a single one, extending between the centres of the two horizontal surfaces of the tail. The side-to-side balance was maintained by ailerons in the form of wing tips set at the outer rear edges of the main planes. The tips were hinged and connected with wires which led to the lever that worked the elevating rudder. Thus by pulling this lever toward him the operator tilted the rudder up, and the machine rose, and by moving it from side to side the biplane was kept on an even keel. For instance, if the machine were to tip to the right he would move the lever to the left, pulling _down_ the hinged ailerons on the right. The ones on the left would still remain standing straight out at the same angle as the main planes. The increase in the lifting power on the right side would cause that end to rise, righting the machine. Most Farman biplanes these days are driven by the well known 7-cylinder Gnome rotary air-cooled engines, set at the rear of the main plane. They are directly connected with the single propeller, which is 8-1/2 feet in diameter. The seat for the aviator is in front of the engine at the front edge of the lower plane, and there also frequently are placed seats for two other passengers. The machine is mounted on wheels and skids. The "Farman Militaire" type is one of the largest and heaviest machines made to date, having a total area of supporting plane of 540 square feet. The chief difference is that instead of two direction rudders there are three, and that the lower main plane is set at a dihedral angle. It was on such a machine ("Type Michelin") that Farman flew steadily for eight and a half hours. It also has made remarkable distance, endurance, and weight-carrying records, although it is a slow machine, making but 34 to 35 miles an hour. The "Type Michelin" is distinguished by the fact that the upper main plane has a spread of 49 feet, 3 inches, while the lower plane had a spread of only 36 feet. MAURICE FARMAN BIPLANE