ACTIVITIES 35 



mountain, town or city. Index maps showing the location and 

 names of quadrangles mapped in any state or region are pub- 

 lished. 



In addition to regular topographic atlas sheets many special 

 topographic maps have been published of areas having par- 

 ticular interest, such as large cities and their environs, or re- 

 gions embracing natural wonders. The Survey has also been 

 engaged for some time in participating in the preparation of 

 the United States portion of the millionth scale map of the 

 world — that is, a map having a scale of one to one million, or 

 a scale of about sixteen miles to the inch. This map is to be 

 part of an international map of the world upon a uniform 

 scale. A few sheets of this map have already been published 

 by the Survey. A number of base maps of the several states 

 and of the United States are also published by the Survey. 



Historically considered, the topographic maps produced by 

 the Survey are primarily of use to the Survey itself as neces- 

 sary bases for geologic maps, but they are now to be regarded 

 as the basic and standard topographic maps of the country for 

 all purposes. They are used by virtually all departments of 

 the national, state, and local governments in the location of 

 field offices, the determination of the boundaries of adminis- 

 trative districts and the consideration of projects for public 

 works, a use in which they are of special value. Before these 

 maps were made, for example, every city was obliged to spend 

 large sums in surveys for water supply. These topographic 

 maps now furnish all necessary data for a far larger area than 

 would be embraced in a local survey. In engineering works, 

 whether municipal or constructed by private capital, and in 

 industrial, mining, and agricultural operations of every sort, 

 the Survey's topographic maps are also of the highest value. 

 The maps are widely used, moreover, in traveling and in 

 countless other activities of every-day life. The extent of 

 their use is indicated by the annual sales, which now amount 

 to over half a million copies. 



Attention should be called to the especial value which at- 



