NOTE.—These maps, projected without reference to political divisions, are designated by some prominent feature found on them. Three scales are used, 1:162500. 1:125000, and 1:250000. These correspond, approximately, to 1 mile, 2 miles, and 4 miles to 1 linear inch on the map. The size, unless otherwise given, is about 20 by 16 inches. They are issued as working editions for the use of geologists of the United States Geological Survey, and are not published for general distribution or for sale. About 900 sheets have been produced since 1883, covering, more or less, every State and Territory except Alaska. Massachusetts, Rhode Island. New Jersey, and the District of Columbia are completely mapped.