=The deRam Camera.=—The only completely automatic plate camera actually produced commercially before the end of hostilities was the French model deRam (Fig. 54). Its plate-changing action has already been described in connection with the American semi-automatic model (Figs. 52, 90 and 91). It differs from the American model in the shutter, which is of the self-capping variety, carried on a rising and falling frame; and in the exposing mechanism. The latter embodies a clutch whose point of attachment to a uniformly rotating disc in the camera is governed through a Bowden wire, whereby the interval between the plate-changing operation and the shutter release is varied. The intervals are indicated by figures on the dial to which the observer's end of the Bowden wire is attached. The source of power for the camera is a constant speed propeller. Complete semi-automatic operation is not possible, as an interval of 1 to 2 seconds elapses between the time a single exposure is called for and its occurrence. No arrangement is provided for hand operation. It will be noted that while this camera is a true automatic apparatus it does not meet even a majority of the requirements listed above as found desirable by experience. There exists a great opportunity for designing and developing an entirely satisfactory automatic plate camera—provided it is agreed that anything more than semi-automatic operation is ever advisable for plates. CHAPTER XI AERIAL FILM CAMERAS The weight of the glass and the sheaths in the plate camera forms its most serious drawback. This weight must be reckoned at least three quarters of a pound for each 18 × 24 centimeter plate. Consequently, with the use of these large plates, and with the demands for ever increasing numbers of pictures to be taken on long reconnaissance flights, a serious conflict arises between the weight of the photographic equipment and the carrying capacity of the plane. Among plate cameras probably the most economical in weight is the deRam. It carries fifty 18 × 24 centimeter plates, and has a total weight of approximately 100 pounds. An advance to 100 or 200 plates—not feasible in the deRam construction—even if we assume the lightest possible magazines, would bring the weight of camera and plates to 150 or 200 pounds, which would be detrimental to the balance and would seriously infringe on the fuel carrying capacity and ceiling of any ordinary reconnaissance plane.