With its space for five or more passengers, and with its low speed, the modern flying boat affords an excellent craft for photographic work. There is ample room for any size of camera, and for any style of mounting, if we assume that there is no objection to an opening in the bottom. The low ceiling of these ships, however, prevents their use for certain forms of aerial photography which should be of the greatest importance. Operations against shore stations—harbors, docks, shipyards, ships at anchor, and fortifications—cannot be undertaken for fear of anti-aircraft guns and hostile land planes. The solution of the problem of carrying and launching fast high flying planes from ships will immediately extend the usefulness of aerial photography to coastal work. In the recent war, such of this as was done, along the Belgian coast—the shore batteries, and the results of naval operations at Zeebrugge and Ostend—was done by land planes from territory held by the Allies. The photographic equipment of sea planes of the type suggested will of course present special problems, but the apparatus used will be apt to approximate closely to that of the land planes. VII THE FUTURE OF AERIAL PHOTOGRAPHY CHAPTER XXXI FUTURE DEVELOPMENTS IN APPARATUS AND METHODS Prophecy is an undertaking that always involves risk. The prophet's guess of what the future will bring forth is based only on the tendencies of the past, the most urgent needs of the present, and the activity of his imagination. He may easily—and he usually does—entirely overlook certain possibilities which may arise apparently from nowhere and which profoundly affect the whole trend of development. Conditions which dominate at the present time—such as military necessity—may happily drop into the background and free the science from some of its severest restrictions. With this caution, some future possibilities in apparatus and methods may be presented along the lines already used in discussing the present status of aerial photography. =Lenses.=—From the military standpoint the next steps in lens design would be toward telephoto lenses on the one hand, and on the other toward lenses of short focus and wide angle. The telephoto lenses used for spotting would be of long equivalent focus—a meter and more—but of handy size, that is, not more than 50 centimeters over all working distance. The wide angle short focus lenses would be designed for low flying reconnaissance or quick mapping work. They would also be demanded for peace-time mapping projects, where the largest possible amount of territory should be covered in a single flight. Both types of lens should be pushed to the extreme in aperture, for short exposures and the maximum of working days will always be demanded.