Single seater or scout planes do not lend themselves to the insertion of such standardized uprights and cross-pieces, because of their small size and the common utilization of all space inside the fuselage for gasoline tanks and control wires. Some French scouts, whose fuselages are very wide, due to the rotary engines, have been fitted with compartments for contemplated automatic film cameras. The most commonly used camera in the single seater was, however, the Italian 24-plate single-motion apparatus (Fig. 49). This camera and its carrying tray occupy very little lateral space and have in actual practice been carried beneath the seat or pushed up through an opening in the bottom of the fuselage under the gasoline tank. Whatever criticism may be made of the adequacy of the mounting, it must be said that the camera, as used, is perhaps the most eminently practical of all developed in the war, as its use on scouts testifies. [Illustration: FIG. 96.—U. S. type “K” film camera on bell-crank mount, in camera bay of DeHaviland 4. Veneer frame at top of bay in place of usual cross-wires.] [Illustration: FIG. 97.—Section of fuselage of veneer construction affording superior accessibility to camera.] =Special Photographic Planes.=—As cameras grew in size, the difficulty of installing them in planes built without regard to photographic requirements greatly increased. Few planes could carry even the 50 centimeter focus camera obliquely without the necessity of poking its nose through the side where it would catch wind and oil; while the 120 centimeter camera could be carried obliquely only in the fore and aft position. Even vertical installation of the latter camera was really feasible in but few planes; sometimes the camera was carried to the exclusion of the observer—and, in fact, this size was never used by the English, whose fuselages were small in cross-section. This situation led, late in the war, to steps toward producing planes designed primarily for photographic reconnaissance. In these the camera would be entirely accessible, and cameras of any size could be carried in any desired position. One scheme which properly belongs under this heading was the provision of a special removable photographic cockpit, for the front or nose of a twin-motored three seater. Other noses, for bombing and heavy machine guns, were also planned, all to be interchangeable. Since the regular photographic bay with uprights and cross-pieces was also provided to the rear, this special photographic ship could on occasion do two classes of work, such as long focus spotting and short focus mapping.