The polyconic projection employs an infinite number of tangent cones. The starting

point for these cones is at the middle parallel or latitude of the area mapped.

4. See 267.

^^^ GRAPHIC PRESENTATION

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Kcuffel H Essrr Co , New York City.

Map Measuring Device.

This instrument is used to measure lines and distances on a map. The small wheel follows the line and the distance is recorded on the dial in inches or centimeters.

maps made for individual states and distributed without charge are used in ordering specific sections. Geologic maps for many sections of the United States and Alaska.

Coast and Geodetic Survey, U. S. Department of Commerce. Navigational charts of the coasts of the United States and its possessions. Air route maps covering the entire United States.

General Land Office, U. S. Department of Interior. Wall map of the United States showing the national parks, national monuments, and other useful information. Maps of the 29 public-land states, Alaska, and Hawaii.

Hydrograpfiic Office, Bureau of Navigation, U. S. Department of ttie Navy. Maps and charts required in navigation in foreign waters and on high seas.

Corps of Engineers, U. S. Army, Engineer Reproduction Plant, Fort Humpfireys, D. C. Special topographic maps of areas of military importance. Some topographic maps not covered by the Geological Survey.

Forest Service, U. S. Department of Agriculture. Geographic maps of national forests. Topographic maps of portions of them.

Bureau of Reclamation, U. S. Department of Interior. Topographic maps of many federal irrigation projects.