GENERAL ASPECTS OF THE SURFACE AS SEEN FROM THE AIR
(FIGS. 12 TO 18)
[Illustration: FIG. 12--Benning, D.C., and the Anacostia River, showing,
from right to left, cultivated lands 40 to 20 feet above sea level, an
elevation too slight to be shown in a vertical photograph; a brushy
slope running from 20 feet to sea level; and marshland along the stream.
The checkered pattern of the upland fields is caused by
different-colored crops. Shocks of corn, spaced evenly in rows,
buildings and shade trees, and light-colored roads and a race track are
shown. The light-colored areas along the stream are occupied by tidal
marsh and are free from brush but covered with vegetation of annual
growth. The figure is one of the photographs used to make the mosaic
shown on Fig. 13. It should be compared with Fig. 13 and with the
topographic map, Fig. 14. Scale, 1: 11,000.]
When a region is viewed from an altitude of several thousand feet the
observer can readily imagine himself looking down on a large map. The
chief features stand out prominently, the smaller to a lesser degree.
Mountains, rivers, and the seashore are
[Illustration: FIG. 13]
[Illustration: FIG. 14]
[Illustration: FIG. 13--Vertical photograph of the land along the
Anacostia River on the eastern edge of Washington, D.C., made up of
several photographs matched together and adjusted to points located by
ordinary survey methods, and reduced in size to correspond with the map,
Fig. 14. The photographs were taken from an airplane with a so-called
mapping camera at such intervals of time that the prints overlap, thus
making it possible to adjust them to each other and to form a continuous
picture of the area. The region shown is the site of improvements that
are at present under way, mainly the regulation of the Anacostia River.
The channel has been widened by dredging and part of the bordering marsh
areas filled in. The photograph shows that this work had progressed to
the Benning Road bridge by the autumn of 1920, when the photograph was
taken, while in 1915, when the area was surveyed for the map, it had
been carried out only as far as the Pennsylvania Avenue bridge. Such
airplane photographs furnish an incomparable tool in the handling of
large-scale engineering projects, both in the study of the territory in
its unimproved state and to follow the progress of the work after
operations are under way. Scale, about 1: 28,000.]
[Illustration: FIG. 14--Part of the topographic map of Washington and
Vicinity, 1: 31,680, published by the U.S. Geological Survey, showing
within the irregular line the same area shown in Fig. 13. Scale, 1:
28,000.]
[Illustration: FIG. 15 (on page 24)--Mosaic of the southeastern part of
Mulberry Island, on the left bank of the James River about 11 miles
northwest of Newport News. Va., showing an area portrayed by many
photographs matched together. Slight differences in shade indicate the
junction of the separate prints. The higher land, about 10 feet above
sea level as determined by surveys on the ground, is shown at the right
by roads and cultivated fields. It is to be noted that roads outline the
dividing line between the high ground and the marsh. At the left are
lower areas of wooded or brushy swampland and of grassy marsh. They
contain a number of abandoned channels: some completely silted up,
others containing small thoroughfares, and still others drained by
meandering streams which seem to have developed after the channels were
definitely abandoned by the streams which originally occupied them.
The streams which drain the marshes have many characteristics of streams
which drain higher lands. They have dendritic patterns, so called from
resemblance to the forking branches of a tree; channels which widen
downstream; and winding or meandering courses. The island terminates in
a long spit composed of silt and fine sand. The banks to the left on
James River are low and marshy: those to the right on Warwick Creek,
except for one small marsh, form low bluffs.
In order that the mosaic may be compared with the map, Fig. 16, it has
been placed with the northerly part at the top of the page, with the
result that, until the page is reversed, the trees in the swampland
appear like hollows in the earth. Scale, 1:14,000.]
especially conspicuous. Streams appear as smooth, winding
ribbons--glistening if the sunlight reflected from them enters the eye,
dark if the bright rays are reflected away from the eye. Railroads can
easily be traced and towns recognized by their form. Concrete roads and
others of light-colored material are plainly visible. Those built of
dark-colored material appear less prominently. Something even of the
character of the forests can be ascertained--whether evenly timbered or
partly of primary and partly of secondary growth; whether intact or
partly burned over; whether consisting chiefly of one species of trees
or of many. The cultivated fields and their relations to roads, streams,
and forests are conspicuous. Towns and cities are spread out like
panoramic views in which are strikingly visible the residence and
manufacturing centers, the layout of streets, the systems of parks, the
position of suburbs, and the relation of these to routes of
transportation and travel--roads, railroads, and waterways. These and
many other features of the landscape--swamps, marshes, buildings, trees,
orchards, and many lesser details--are recognizable and are all recorded
on the
[Illustration: FIG. 15. (For explanation, see p. 23.)]
[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.]
[Illustration: FIG. 18--Map of the same area shown in Fig. 17 enlarged
from the corresponding sections of the 1:62,500 Columbus and Seale,
Ga.-Ala., and the 1:125,000 Talbotton and Opelika, Ga.-Ala., topographic
sheets surveyed mainly in 1906 and 1907 and published by the U.S.
Geological Survey. The cross section at the bottom lies along the line
indicated on the map and extends somewhat beyond the right border of the
map. The section shows the broad shelf upon which the city rests and its
relation to the river and to the terraced hillsides east of it. Scale,
1:38,000.]