The technique of night photography may take either of two directions. On one hand we may develop flashes of the requisite intensity to give all their light in 1/100 second; on the other hand, it may prove more feasible to use flashes of longer duration and to arrange for the camera shutter (of the between-the-lens type) to be exposed synchronously with the middle of the flash. One way, frequently suggested, to use these longer flashes would be to trail the charge on a long wire, through which the ignition is effected electrically. This is not likely to be satisfactory, however, for the resistance of a wire is so great that when the plane flies at any practical height, the trailed flash, if it reaches near the ground, will be forced to a very great distance behind. Probably the best solution will involve accurate synchronizing of the fuse in the freely dropped sack of flash powder with the exposing mechanism in the camera. CHAPTER XXXII PICTORIAL AND TECHNICAL USES Aside from their element of novelty, aerial photographs have undoubted qualities of beauty and utility. The “bird's-eye view” has always been a favorite for revealing to the best advantage the entire form and location of buildings and of other large objects. Heretofore such views have usually had to be drawn by an imaginative artist. [Illustration: FIG. 188.—Rheims Cathedral.] Aerial oblique views possess the virtues both of pictures and of plans. They are destined to be extensively used in the study of architecture (Fig. 188). Cathedrals, castles, town halls, particularly those still in their cramped medieval surroundings where they can never be seen in their entirety from the ground, come forth in all their beautiful or quaint proportions from the airman's point of vantage. Stereoscopic aerial views are destined to occupy a valuable position also. Stereo prints of the famous buildings of Europe, taken from the air, will give to the prospective traveler or the arm-chair tourist a many fold more accurate idea of their construction than will any number of mere surface views. [Illustration: FIG. 189.—A portion of Vienna seen from the air, during a “propaganda raid.” Italian official photograph.] [Illustration: FIG. 190.—The Rialto bridge, Venice. Italian Air Service photograph.] [Illustration: FIG. 191.—A partly developed suburb.]