NOTE.—The Geological Survey is making a series of topographic maps that will eventually cover the whole United States, also Alaska and Hawaii. The individual maps are projected to represent quadrangle areas rather than political divisions, and each map is designated by the name of some prominent town or natural feature in the area mapped. The scales most commonly used are 1:31,680, 1:62,500, and 1:125,000, corresponding, approximately, to ½ mile, 1 mile, and 2 miles to 1 inch.
The area covered differs with the latitude, but the average area is 58, 280, or 920 square miles, respectively, for these three scales. Topographic maps are printed on uniform-sized paper, about 20 by 16½ incites, and the maps of the quadrangle areas represented thereon are about 17½ inches long and 12 to 15 inches wide, according to latitude. For some areas of particular importance special large-scale maps are published. A general description of topographic maps and a list of the symbols used are printed on the reverse of each sheet.
About 45 per cent of the area of the country, excluding Alaska, has been mapped, everv State being represented. Connecticut, Delaware, the District of Columbia, Hawaii, Maryland, Massachusetts, New Jersey, New York, Ohio, Rhode Island, and West Virginia are completely mapped. Maps of the regular size are sold by the Geological Survey at 10c. each, but a discount of 40 per cent is allowed on any order which amounts to $5.00 at the retail price. The discount is allowed on an order for either maps or folios alone, or for maps and folios together.