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 without reference to 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 average area covered is about 58, 230, or 920 square miles. For some areas of particular importance special large-scale maps are published. The usual size, exclusive of the margin, is 17.5 inches in height by 11.5 to 16 inches in width, the width varying with the latitude. The standard sheets measure 20 by 16½ inches. A general description of the topographic maps is printed on the reverse of each sheet.
More than two-fifths of the area of the country, excluding Alaska, has been mapped, every State being represented. Connecticut, Delaware, the District of Columbia, 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 or more at the retail price. The discount is allowed on an order for either maps or folios alone or for maps and folios together, but does not apply to a few folios that are sold at 5c. each on account of damage by fire.