The adaptability of the 1:1,000,000 scale map to use as a base for general geologic maps is shown in the geologic maps of the southern peninsula of Michigan and of Indiana in Monograph 53 (Pls. IV and VII), the map of Florida in Bulletin 60 (Pl. I), and the map of Vermont in Water-Supply Paper 424 (Pl. I). 3. The Survey's two-sheet wall map of the United States, 49 by 76 inches, scale 1:2,500,000 (approximately 40 miles to 1 inch). Parts of this map can be used as bases for general geologic or other maps and as copy for index and other small diagrammatic maps. This map is published both with and without contours. 4. Land Office maps and township plats. These maps are now being published on a scale of 12 miles to 1 inch; they are also photo-lithographed on one-half that scale, or 24 miles to 1 inch. The township plats are printed on a scale of one-half mile to 1 inch. The maps are especially useful in compiling maps in which land lines (townships and sections) are essential, and the township plats afford valuable detail and are useful in field work and in revising other maps. Township and section lines should appear on all land-classification maps published by the Survey. On maps on a scale less than 1:250,000 only the townships should be shown; on maps on scales greater than 1:250,000 the sections should be shown; on maps on a scale of 1:250,000 the sections should be shown, unless their representation will materially impair the legibility of the map, in which case only the townships should be shown. (See fig. 1.) 5. Post-route maps, covering single States or groups of adjacent States, published on sheets of different sizes and on scales determined mainly by the size of the State. The map of Texas is published on a scale of 12 miles to 1 inch, that of Virginia on a scale of 7 miles to 1 inch, and that of West Virginia on a scale of 6 miles to 1 inch. Both the Land Office and the post-route maps are useful for reference in compiling maps on smaller scales. Post-route maps are especially useful for comparing and verifying the location of cities, towns, and railroads. 6. Coast and Geodetic Survey charts, published on scales that are governed by the area represented and the amount of detail to be shown. These maps should always be used in compiling and correcting coast lines. 7. Maps and charts published by the Corps of Engineers of the Army, the Mississippi River Commission, the surveys of the Great Lakes, and the boundary surveys. These maps are especially useful if the scale of the map to be compiled requires considerable detail. 8. The Survey's three small base maps of the United States--(_a_) a map 18 by 28 inches, scale 110 miles to 1 inch, which is published both with and without contours, or with relief or hypsometric shading; (_b_) a map 11 by 16 inches, scale 190 miles to 1 inch; (_c_) a map 7-1/2 by 12 inches, scale 260 miles to 1 inch, designed for use as a two-page illustration in a bulletin or a water-supply paper.