the strands will turn free of the backbone, and will make an even line parallel with it. Both hooks should be covered by little pieces of rubber tubing to protect the rubber strands. Any friction whatever in a model is bad, but it is worst of all upon the rubber strands of the motor. With the parts in hand the next step is attaching the planes to the backbone. In this machine the motor should be above the planes, so that the planes should be affixed to the upper side of the central stick, with the rubber strands above them. The propeller is at the rear, so the small front plane should be placed at the front, with the slightly curved edge to the rear. It should be about an inch from the tip of the stick and the front edge should be elevated slightly to give the necessary lifting power. The main plane should be placed about an inch from the rear tip of the backbone, with the curved edge to the rear and the front slightly elevated. The planes should be affixed with rubber bands so that it is possible to move them forward or back, because the little monoplane might be lacking in fore and aft stability and the rearrangement of the planes might correct it. It might even be found more satisfactory in some models to change the order and let the propeller, base, and strands of the motor come below the planes instead of above them. Your own experience will tell best. [Illustration: THE ANTOINETTE MONOPLANE New armoured Antoinette shown in the large picture, while the small insert shows the old-style machine.] [Illustration: Photo by Philip W. Wilcox THE NIEUPORT MONOPLANE Comparatively a new make, the Nieuport monoplane has sprung into great favour for its speed and passenger-carrying capacities.] Of course, the planes must be placed on the backbone exactly evenly or the airship will be lopsided, a fatal fault. By experimenting, the boy can tell just how high the front edges should be elevated, or, in other words, what angle of incidence he should give his plane. A rudder, to keep the machine in a straight course, can be added underneath the centre of the main plane. It should be about two inches square, but shaved off to a curving razor edge. Also light skids of cane or rattan may be added. They should be glued to the under side of the backbone and curved backward like sled runners. The front one should be two and a half to three inches high, while the rear one should be about an inch to an inch and a half less.