[Illustration: FIG. 16--The same area as shown in Fig. 15 reduced from a section of a map on the scale of 1:10,000 by the Corps of Engineers, U.S.A. The photographs shown in Fig. 15 were used for mapping certain small features on this map, such as small streams. Scale, 1:14,000.] photographic negative. So faithfully does the camera reproduce all the horizontal features within its range of vision that it is conceivable that a photograph correctly dated might become a valuable record in cases of boundary disputes or other litigations involving the position of fences, fields, roads, or even streams, at a given date. [Illustration: FIG. 17] [Illustration: FIG. 18] [Illustration: FIG. 17--Columbus. Ga. A part of a mosaic made at Camp Benning near-by in 1909 showing the town, river, and surrounding country. The scale is so small that buildings and trees appear as dots, city blocks as small parallelograms, streets and roads as light-colored lines. The cultivated fields appear as irregularly checkered areas, and the concentric lines of the terraced slopes have the appearance of contour lines on a topographic map (see Fig. 18). The picture illustrates many of the features of city geography. The comparatively straight course of the river and the heavy growth of trees and bushes along its edges indicate a minimum of flood-plain and steep banks--an inference supported by the fact that the principal business center of the city, shown by large, closely set roofs, is built close to the river. Surrounding this section is the most densely populated district, which in the northern part of the city gives way to a district of houses set farther apart and separated by lawns set with trees. Other less extensive business centers are shown as small spots of closely grouped buildings. A variety of suburban types is to be seen: some quite city-like, with a business center, a densely populated residential district, and a district of houses separated by grounds; others more village-like in their lack of a well-developed center but still more or less completely separated from the city proper; still others, sporadic scatterings of houses and grounds extending from the city for some distance along the principal roads. The railroad center is located conveniently near the business center, and the radiating lines of road and railroad communications are in strong contrast to the rectangular arrangement of the city streets. Factories, indicated by large, light-colored roofs, are located along the railroad in the southern part of the city and along the river to the north. Those along the river are operated by power from the falls which the picture shows. The terraced slopes are characteristic of the region, the farmers here and elsewhere in the South making these terraces in their plowed fields to prevent rain water from washing away the soil. Scale, about 1:38,000.]